Studies are listed as Pro, Con, or Not Clearly Pro or Con, based on their conclusions regarding cannabis' potential medical benefit. Extracts, such as Sativex, are derived directly from the plant, and are not synthetically created. Studies involving man-made substances, such as Marinol, Nabilone, Cannabinor, and others were not included in this review. If there are any peer-reviewed studies involving marijuana that we have not included, please let us know.

 "Symptoms relating to spasticity are common in multiple sclerosis (MS) and can be difficult to treat. We have investigated the efficacy, safety and tolerability of a standardized ... cannabis-based medicine (CBM) containing delta-9 tetrahydrocannabinol (THC) and cannabidiol (CBD), upon spasticity in MS. A total of 189 subjects with definite MS and spasticity were randomized to receive daily doses of active preparation (n = 124) or placebo (n = 65) in a double blind study over 6 weeks...

The primary efficacy analysis... showed the active preparation to be significantly superior...

We conclude that this CBM [cannabis-based medicine] may represent a useful new agent for treatment of the symptomatic relief of spasticity in MS."
Mar. 2007 - Christine Collin, MD 

Donald Abrams, MD, Professor of Clinical Medicine at the University of California at San Francisco, et al. wrote in their Feb. 13, 2007 article titled "Cannabis in Painful HIV-Associated Sensory Neuropathy: A Randomized Placebo-Controlled Trial" in the journal Neurology:

"Objective: To determine the effect of smoked cannabis on the neuropathic pain of HIV-associated sensory neuropathy, and an experimental pain model...

Patients were randomly assigned to smoke either cannabis (3.56% thc) or identical placebo cigarettes with the cannabinoids extracted three times daily for 5 days...

Conclusion: Smoked cannabis was well tolerated and effectively relieved chronic neuropathic pain from HIV-associated sensory neuropathy The findings are comparable to oral drugs used for chronic neuropathic pain."
Feb. 13, 2007 - Donald Abrams, MD 

Ileana Tomida, MD, Ophthalmology Specialist, et al. wrote in an Oct. 2006 article titled "Effect of Sublingual Application of Cannabinoids on Intraocular Pressure: A Pilot Study" in the Journal of Glaucoma:

"PURPOSE: The purpose of this study was to assess the effect on intraocular pressure (IOP) and the safety and tolerability of oromucosal administration of a low dose of delta-9-tetrahydrocannabinol (Delta-9-THC) and cannabidiol (CBD)...

CONCLUSIONS: A single 5 mg sublingual dose of Delta-9-THC reduced the IOP temporarily and was well tolerated by most patients. Sublingual administration of 20 mg CBD did not reduce IOP, whereas 40 mg CBD produced a transient increase IOP rise."
Oct. 2006 - Ileana Tomida, MD 

Not Clearly Pro or Con

Florian Strasser, MD, Assistant Medical Director of the Swiss Society of Palliative Care et al., wrote in a July 2006 article titled "Comparison of Orally Administered Cannabis Extract and Delta-9-Tetrahydrocannabinol in Treating Patients with Cancer-Related Anorexia-Cachexia Syndrome: A Multicenter, Phase III, Randomized, Double-Blind, Placebo-Controlled Clinical Trial From The Cannabis-in-Cachexia-Study-Group" in the Journal of Clinical Oncology:

"PURPOSE: To compare the effects of cannabis extract (CE), delta-9-tetrahydrocannabinol (THC), and placebo (PL) on appetite and quality of life (QOL) in patients with cancer-related anorexia-cachexia syndrome (CACS)...

 

CONCLUSION: CE at the oral dose administered was well tolerated by these patients with CACS. No differences in patients' appetite or QOL were found either between CE, THC, and PL or between CE and THC at the dosages investigated."
July 2006 - Florian Strasser, MD 

Not Clearly Pro or Con

John P. Zajicek, PhD, Professor of Clinical Neuroscience at the Neurology Research and Clinical Trials Unit of the Peninsula Medical School at the University of Plymouth, et al., wrote the following in a Dec. 2005 article titled "Cannabinoids in Multiple Sclerosis (CAMS) Study: Safety and Efficacy Data for 12 Months Follow Up" in the Journal of Neurology, Neurosurgery and Psychiatry:

"OBJECTIVE: To test the effectiveness and long term safety of cannabinoids in multiple sclerosis (MS), in a follow up to the main Cannabinoids in Multiple Sclerosis (CAMS) study...

RESULTS: Intention to treat analysis of data from the 80% of patients followed up for 12 months showed evidence of a small treatment effect on muscle spasticity as measured by change in Ashworth score from baseline to 12 months...There was suggestive evidence for treatment effects of Delta(9)-THC on some aspects of disability. There were no major safety concerns. Overall, patients felt that these drugs were helpful in treating their disease...

CONCLUSIONS: These data provide limited evidence for a longer term treatment effect of cannabinoids. A long term placebo controlled study is now needed to establish whether cannabinoids may have a role beyond symptom amelioration in MS."
Dec. 2005 - John P. Zajicek, PhD 

Not Clearly Pro or Con

David J. Rog, PhD, from the Walton Centre for Neurology and Neurosurgery at the University of Liverpool, et al., wrote in a Sep. 2005 article titled "Randomized, Controlled Trial of Cannabis-Based Medicine in Central Pain in Multiple Sclerosis" in the journal Neurology:

"BACKGROUND: Central pain in multiple sclerosis (MS) is common and often refractory to treatment...

CONCLUSIONS: Cannabis-based medicine is effective in reducing pain and sleep disturbance in patients with multiple sclerosis related central neuropathic pain and is mostly well tolerated."
Sep. 2005 - David J. Rog, PhD 

Pro

Jonathan S. Berman, MA, Consulting Anaesthetist at the Royal National Orthopaedic Hospital, et al., wrote the following in a Dec. 2004 article titled "Efficacy of Two Cannabis Based Medicinal Extracts for Relief of Central Neuropathic Pain from Brachial Plexus Avulsion: Results of a Randomised Controlled Trial" in the journal Pain:

"The objective was to investigate the effectiveness of cannabis-based medicines for treatment of chronic pain associated with brachial plexus root avulsion. This condition is an excellent human model of central neuropathic pain as it represents an unusually homogenous group in terms of anatomical location of injury, pain descriptions and patient demographics...

The primary outcome measure was the mean pain severity score during the last 7 days of treatment. Secondary outcome measures included pain related quality of life assessments. The primary outcome measure failed to fall by the two points defined in our hypothesis. However, both this measure and measures of sleep showed statistically significant improvements.

The study medications were generally well tolerated with the majority of adverse events, including intoxication type reactions, being mild to moderate in severity and resolving spontaneously. Studies of longer duration in neuropathic pain are required to confirm a clinically relevant, improvement in the treatment of this condition."
Dec. 2004 - Jonathan S. Berman, MA 

Pro

Camille B. Carroll, PhD, Clinical Research Fellow at the Peninsula College of Medicine and Dentistry, et al., wrote in an Oct. 2004 article titled "Cannabis For Dyskinesia In Parkinson Disease: A Randomized Double-blind Crossover Study" in the journal Neurology:

"Seventeen patients completed the RCT. Cannabis was well tolerated, and had no pro- or antiparkinsonian action. There was no evidence for a treatment effect on levodopa-induced dyskinesia as assessed by the UPDRS, or any of the secondary outcome measures.

CONCLUSIONS: Orally administered cannabis extract resulted in no objective or subjective improvement in dyskinesias or parkinsonism."
Oct. 2004 - Camille B. Carroll, PhD 

Derick T. Wade, MD, Professor in the Department of Clinical Neurology at the University of Oxford, et al., wrote the following in an Aug. 2004 article titled "Do Cannabis-based Medicinal Extracts Have General Or Specific Effects on Symptoms in Multiple Sclerosis? A Double-blind, Randomized, Placebo-controlled Study on 160 Patients," published in the journal Multiple Sclerosis:

"The primary outcome measure was a Visual Analogue Scale (VAS) score for each patient's most troublesome symptom. Additional measures included VAS scores of other symptoms, and measures of disability, cognition, mood, sleep and fatigue. Following CBME the primary symptom score reduced from mean (SE) 74.36 (11.1) to 48.89 (22.0) following CBME and from 74.31 (12.5) to 54.79 (26.3) following placebo [ns].

Spasticity VAS scores were significantly reduced by CBME (Sativex) in comparison with placebo (P=0.001). There were no significant adverse effects on cognition or mood and intoxication was generally mild."
Aug. 2004 - Derick T. Wade, MD

Claude Vaney, MD, Medical Director of the Neurological Rehabilitation and MS Centre, Montana, Switzerland, et al., wrote in an Aug. 2004 article titled "Efficacy of Tetrahydrocannabinol in Patients Refractory to Standard Antiemetic Therapy. Efficacy, Safety and Tolerability of an Orally Administered Cannabis Extract in the Treatment of Spasticity in Patients with Multiple Sclerosis: A Randomized, Double-blind, Placebo-controlled, Crossover Study" in the journal Multiple Sclerosis:

"In the 50 patients included into the intention-to-treat analysis set, there were no statistically significant differences associated with active treatment compared to placebo, but trends in favour of active treatment were seen for spasm frequency, mobility and getting to sleep.

In the 37 patients (per-protocol set) who received at least 90% of their prescribed dose, improvements in spasm frequency (P = 0.013) and mobility after excluding a patient who fell and stopped walking were seen (P = 0.01). Minor adverse events were slightly more frequent and severe during active treatment, and toxicity symptoms, which were generally mild, were more pronounced in the active phase.

CONCLUSION: A standardized Cannabis sativa plant extract might lower spasm frequency and increase mobility with tolerable side effects in MS patients with persistent spasticity not responding to other drugs."
Aug. 2004 - Claude Vaney, MD 

Patrick Fox, MD, Clinical Neurologist at the Peninsula Medical School at the University of Plymouth, et al., wrote in an Apr. 2004 article titled "The Effect of Cannabis on Tremor in Patients with Multiple Sclerosis" in the journal Neurology:

"BACKGROUND: Disabling tremor is common in patients with multiple sclerosis (MS). Data from animal model experiments and subjective and small objective studies involving patients suggest that cannabis may be an effective treatment for tremor associated with MS. To our knowledge, there are no published double-blind randomized controlled trials of cannabis as a treatment for tremor in MS patients...

RESULTS: Analysis of the data showed no significant improvement in any of the objective measures of upper limb tremor with cannabis extract compared to placebo. Finger tapping was faster on placebo compared to cannabis extract (p < 0.02). However, there was a nonsignificant trend for patients to experience more subjective relief from their tremors while on cannabis extract compared to placebo.

CONCLUSIONS: Cannabis extract does not produce a functionally significant improvement in MS-associated tremor."
Apr. 2004 - Patrick Fox, MD 

Not Clearly Pro or Con

Derick T. Wade, MD, Professor in the Department of Clinical Neurology at the University of Oxford, et al., wrote in a Feb. 2003 article titled "A Preliminary Controlled Study to Determine Whether Whole-Plant Cannabis Extracts Can Improve Intractable Neurogenic Symptoms" in the journal Clinical Rehabilitation:

"OBJECTIVES: To determine whether plant-derived cannabis medicinal extracts (CME) can alleviate neurogenic symptoms unresponsive to standard treatment, and to quantify adverse effects...

Measures used: Patients recorded symptom, well-being and intoxication scores on a daily basis using visual analogue scales. At the end of each two-week period an observer rated severity and frequency of symptoms on numerical rating scales, administered standard measures of disability (Barthel Index), mood and cognition, and recorded adverse events.

RESULTS: Pain relief associated with both THC and CBD was significantly superior to placebo. Impaired bladder control, muscle spasms and spasticity were improved by CME in some patients with these symptoms. Three patients had transient hypotension and intoxication with rapid initial dosing of THC-containing CME.

CONCLUSIONS: Cannabis medicinal extracts can improve neurogenic symptoms unresponsive to standard treatments. Unwanted effects are predictable and generally well tolerated. Larger scale studies are warranted to confirm these findings."
Feb. 2003 - Derick T. Wade, MD 

Pro

May 2002
Neurology
Vol. 58, Issue 9, Pages 1404-1407

"The authors conducted a randomized, double-blind, placebo-controlled, twofold crossover study in 16 patients with MS who presented with severe spasticity to investigate safety, tolerability, and efficacy of oral Delta(9)-Tetrahydrocannabinol (THC) and Cannabis sativa plant extract. Both drugs were safe, but adverse events were more common with plant-extract treatment. Compared with placebo, neither THC nor plant-extract treatment reduced spasticity. Both THC and plant-extract treatment worsened the participant's global impression."
May 2002 - Joep Killestein, MD, PhD 

Con

Harry S. Greenberg, MD, Professor in the Department of Neurology at the University of Michigan, et al., wrote the following in their Mar. 1994 article titled "Short-term Effects of Smoking Marijuana on Balance in Patients with Multiple Sclerosis and Normal Volunteers," published in the journal Clinical Pharmacology and Therapeutics:

"A double-blind randomised placebo-controlled study of inhaled marijuana smoke on postural responses was performed in 10 adult patients with spastic multiple sclerosis (MS) and 10 normal volunteers matched as closely as possible for age, sex, and weight. A computer-controlled dynamic posturographic platform with a video line scan camera measured shoulder displacement in response to pseudorandom platform movements.

Pre-marijuana smoking patient tracking was inferior to that of the normal volunteers as indicated by the higher noise variance of the former.

Smoking one marijuana cigarette containing 1.54% Delta-9-tetrahydrocannabinol increased postural tracking error in both the patients and normal control subjects with both eyes open and closed; this untoward effect was greatest for the patients. The tracking error was also accompanied by a decrease in response speed for the patients with their eyes closed.

Marijuana smoking further impairs posture and balance in patients with spastic MS."
Mar. 1994 - Harry S. Greenberg, MD 

Paul F. Consroe, PhD, Professor Emeritus in the Department of Pharmacology and Toxicology at the University of Arizona, et al., wrote the following in their Nov. 1991 article titled "Controlled Clinical Trial of Cannabidiol in Huntington's Disease," published in the journal Pharmacology, Biochemistry and Behavior:

"Based on encouraging preliminary findings, cannabidiol (CBD), a major nonpsychotropic constituent of Cannabis, was evaluated for symptomatic efficacy and safety in 15 neuroleptic-free patients with Huntington's Disease (HD). The effects of oral CBD (10 mg/kg/day for 6 weeks) and placebo (sesame oil for 6 weeks) were ascertained weekly under a double-blind, randomized cross-over design...

In summary, CBD, at an average daily dose of about 700 mg/day for 6 weeks, was neither symptomatically effective nor toxic, relative to placebo, in neuroleptic-free patients with HD."
Nov. 1991 - Paul F. Consroe, PhD 

Not Clearly Pro or Con

W. Murray Thomson, PhD, Professor of Dental Epidemiology and Public Health at Sir John Walsh Research Institute, et al., wrote the following in their Feb. 6, 2008 study titled "Cannabis Smoking and Periodontal Disease Among Young Adults," published in the Journal of the American Medical Association:

"Design and Setting: Prospective cohort study of the general population, with cannabis use determined at ages 18, 21, 26, and 32 years and dental examinations conducted at ages 26 and 32 years. The most recent data collection (at age 32 years) was completed in June 2005.

Participants: A complete birth cohort born in 1972 and 1973 in Dunedin, New Zealand, and assessed periodically (with a 96% follow-up rate of the 1015 participants who survived to age 32 years). Complete data for this analysis were available from 903 participants (comprising 89.0% of the surviving birth cohort).

The study's demonstration of a strong association between cannabis use and periodontitis experience by age 32 years indicates that long-term smoking of cannabis is detrimental to the periodontal tissues and that public health measures to reduce the prevalence of cannabis smoking may have periodontal benefits for the population. [...]

Although definitively establishing the periodontal effects of exposure to cannabis smoke should await confirmation in other populations and settings, health promoters and dental and medical practitioners should take steps to raise awareness of the strong probability that regular cannabis users may be doing damage to the tissues that support their teeth."
Feb. 6, 2008 - W. Murray Thomson, PhD 

Con

Burkhard Hinz, PhD, Director of the Institute of Toxicology and Pharmacology at the University of Rostock in Germany, et al., wrote the following in a Dec. 25, 2007 article titled "Inhibition of Cancer Cell Invasion by Cannabinoids via Increased Expression of Tissue Inhibitor of Matrix Metalloproteinases-1," published in the Journal of the National Cancer Institute:

"Prior knowledge
Treatment with cannabinoids had been shown to reduce the invasiveness of cancer cells, but the cellular mechanisms underlying this effect were unclear.

Study design
Cancer cells treated with combinations of cannabinoids, antagonists of cannabinoid receptors, and siRNA to tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) were assessed for invasiveness, protein expression, and activation of signal transduction pathways.

Contribution
The expression of TIMP-1 was shown to be stimulated by cannabinoid receptor activation and to mediate the anti-invasive effect of cannabinoids.

Implications
Clarification of the mechanism of cannabinoid action may help investigators to explore their therapeutic benefit.

Limitations
The relevance of the findings to the behavior of tumor cells in vivo remains to be determined."
Dec. 25, 2007 - Burkhard Hinz, PhD 

[Editor's Note: Although this study was not conducted on humans, it was performed using human cells in a test tube which is why we have classified it under the "Human Studies" category.]

Pro

Margaret Haney, PhD, Associate Professor of Clinical Neuroscience at Columbia University, et al., wrote the following in their Aug. 15, 2007 study titled "Dronabinol and Marijuana in HIV-Positive Marijuana Smokers: Caloric Intake, Mood, and Sleep," published in the Journal of Acquired Immune Deficiency Syndromes:

"Objectives: This placebo-controlled within-subjects study evaluated marijuana and dronabinol across a range of behaviors: eating topography, mood, cognitive performance, physiologic measures, and sleep.

Methods: HIV-positive marijuana smokers (n = 10) completed 2 16-day inpatient phases. Each dronabinol (5 and 10 mg) and marijuana (2.0% and 3.9% [DELTA]9-tetrahydrocannabinol [THC]) dose was administered 4 times daily for 4 days, but only 1 drug was active per day, thereby maintaining double-blind dosing. Four days of placebo washout separated each active cannabinoid condition.

Results: As compared with placebo, marijuana and dronabinol dose dependently increased daily caloric intake and body weight in HIV-positive marijuana smokers. All cannabinoid conditions produced significant intoxication, except for low-dose dronabinol (5 mg); the intoxication was rated positively (eg, "good drug effect") with little evidence of discomfort and no impairment of cognitive performance. Effects of marijuana and dronabinol were comparable, except that only marijuana (3.9% THC) improved ratings of sleep.

Conclusions: These data suggest that for HIV-positive marijuana smokers, both dronabinol (at doses 8 times current recommendations) and marijuana were well tolerated and produced substantial and comparable increases in food intake."
Aug. 15, 2007 - Margaret Haney, PhD 

Pro

Theresa H. M. Moore, MSc, Research Associate in the Department of Social Medicine at the University of Bristol, and Stanley Zammit, PhD, Clinical Lecturer in the Department of Psychological Medicine at Cardiff University, et al., stated the following in their July 27, 2008 article titled "Cannabis Use and Risk of Psychotic or Affective Mental Health Outcomes: A Systematic Review," published in the Lancet:

"There was an increased risk of any psychotic outcome in individuals who had ever used cannabis... A substantial confounding effect was present for both psychotic and affective outcomes...

The evidence is consistent with the view that cannabis increases risk of psychotic outcomes independently of confounding and transient intoxication effects, although evidence for affective outcomes is less strong. The uncertainty about whether cannabis causes psychosis is unlikely to be resolved by further longitudinal studies such as those reviewed here. However, we conclude that there is now sufficient evidence to warn young people that using cannabis could increase their risk of developing a psychotic illness later in life."
July 27, 2007 - Theresa Moore, MSc  Stanley Zammit, PhD 

Con

Antonio W. Zuardi, PhD, Vice Director of the Department of Neurology at the University of São Paulo, et al., wrote in a Sep. 2006 article titled "Cannabidiol Monotherapy for Treatment-Resistant Schizophrenia" in the Journal of Psychopharmacology:

"Cannabidiol (CBD), one of the major products of the marijuana plant, is devoid of marijuana's typical psychological effects. In contrast, potential antipsychotic efficacy has been suggested based on preclinical and clinical data (Zuardi et al., 2002). In this report, we further investigated the efficacy and safety of CBD monotherapy in three patients with treatment-resistant schizophrenia (TRS)...

Efficacy, tolerability and side effects were assessed. One patient showed mild improvement, but two patients didn't show any improvement during CBD monotherapy. All patients tolerated CBD very well and no side effects were reported. These preliminary data suggest that CBD monotherapy may not be effective for TRS."
Sep. 2006 - Antonio W. Zuardi, PhD 

Con

David M. Fergusson, PhD, Research Professor of the Department of Psychological Medicine at the University of Otago, et al., wrote the following in a Mar. 2005 article titled "Tests of Causal Linkages Between Cannabis Use and Psychotic Symptoms," published in the journal Addiction:

"Regression models adjusting for observed and non-observed confounding suggested that daily users of cannabis had rates of psychotic symptoms that were between 1.6 and 1.8 times higher than non-users of cannabis....

The results of the present study add to a growing body of evidence suggesting that regular cannabis use may increase risks of psychosis.

The present study suggests that:
(a) the association between cannabis use and psychotic symptoms is unlikely to be due to confounding factors; and
(b) the direction of causality is from cannabis use to psychotic symptoms."
Mar. 2005 - David M. Fergusson, PhD 

Con

Maria L. de Ceballos, PhD, Researcher and Group Leader of the Department of Neural Plasticity at the Cajal Institute, Spain, et al., wrote the following in a Feb. 2005 article titled "Prevention of Alzheimer's Disease Pathology by Cannabinoids: Neuroprotection Mediated by Blockage of Microglial Activation," published in the Journal of Neuroscience:

"Our results indicate that cannabinoid receptors are important in the pathology of AD [Alzheimer's Disease] and that cannabinoids succeed in preventing the neurodegenerative process occurring in the disease."
Feb. 2005 - Maria L. de Ceballos, PhD 

Jason Schiffman, PhD, Associate Professor of Clinical Psychology at the University of Hawaii at Manoa, et al., wrote the following in their Jan. 2005 article titled "Symptoms of Schizotypy Precede Cannabis Use," published in the journal Psychiatric Research:

"Findings suggest that regular cannabis users are significantly more prone to cognitive and perceptual distortions as well as disorganization, but not interpersonal deficits, than non-regular users and those who have never used.

Additionally, the onset of schizotypal symptoms generally precedes the onset of cannabis use. The findings do not support a causal link between cannabis use and schizotypal traits."
Jan. 2005 - Jason Schiffman, PhD 

Not Clearly Pro or Con

Researchers from the Movement Disorders Centre, Department of Neurology at Charles University, Prague, Czech Republic, wrote in their Sep. 2004 article "Survey on Cannabis Use in Parkinson's Disease," published in the journal Movement Disorders:

"An anonymous questionnaire sent to all patients attending the Prague Movement Disorder Centre revealed that 25% of 339 respondents had taken cannabis and 45.9% of these described some form of benefit....

The late onset of cannabis action is noteworthy. Because most patients reported that improvement occurred approximately two months after the first use of cannabis, it is very unlikely that it could be attributed to a placebo reaction."
Sep. 2004 - Movement Disorders 

Pro

Ciaran M. Brady, Specialist Registrar in Urology at Edith Cavell Hospital, et al., wrote the following in an Aug. 2004 article titled "An Open-Label Pilot Study of Cannabis-based Extracts for Bladder Dysfunction in Advanced Multiple Sclerosis," published in the journal Multiple Sclerosis:

"The majority of patients with multiple sclerosis (MS) develop troublesome lower urinary tract symptoms (LUTS). Anecdotal reports suggest that cannabis may alleviate LUTS, and cannabinoid receptors in the bladder and nervous system are potential pharmacological targets. In an open trial we evaluated the safety, tolerability, dose range, and efficacy of two whole-plant extracts of Cannabis sativa in patients with advanced MS and refractory LUTS."

"Urinary urgency, the number and volume of incontinence episodes, frequency and nocturia all decreased significantly following treatment (P <0.05, Wilcoxon's signed rank test). However, daily total voided, catheterized and urinary incontinence pad weights also decreased significantly on both extracts. Patient self-assessment of pain, spasticity and quality of sleep improved significantly (P <0.05, Wilcoxon's signed rank test) with pain improvement continuing up to median of 35 weeks.

There were few troublesome side effects, suggesting that cannabis-based medicinal extracts are a safe and effective treatment for urinary and other problems in patients with advanced MS."
Aug. 2004 - Ciaran M. Brady 

Pro

K. L. L. Movig, et al., wrote the following in their article titled "Psychoactive Substance Use and the Risk of Motor Vehicle Accidents," published in the journal Accident Analysis & Prevention:

"The objective of this study was to estimate the association between psychoactive drug use and motor vehicle accidents requiring hospitalization...

The risk for road trauma was increased for single use of benzodiazepines and alcohol... High relative risks were estimated for drivers using combinations of drugs and those using a combination of drugs and alcohol. Increased risks, although not statistically significant, were assessed for drivers using amphetamines, cocaine, or opiates.

No increased risk for road trauma was found for drivers exposed to cannabis."
July 2004 - Accident Analysis & Prevention 

John Macleod, PhD, MSc, Senior Lecturer in Primary Care in the Department of Primary Care and General Practice at the University of Birmingham, et al., wrote the following in their article "Psychological and Social Sequelae of Cannabis and Other Illicit Drug Use by Young People: A Systematic Review of Longitudinal, General Population Studies," published May 15, 2004 in the Lancet:

"Available evidence does not strongly support an important causal relation between cannabis use by young people and psychosocial harm, but cannot exclude the possibility that such a relation exists.

The lack of evidence of robust causal relations prevents the attribution of public health detriments to illicit drug use. In view of the extent of illicit drug use, better evidence is needed."
May 15, 2004 - John Macleod, PhD 

Wilson M. Compton, MD, et al., wrote the following in their May 2004 article "Prevalence of Marijuana Use Disorders in the United States: 1991-1992 and 2001-2002," published in the Journal of the American Medical Association (JAMA):

"Among the adult U.S. population, the prevalence of marijuana use remained stable at about 4.0% over the past decade. In contrast, the prevalence of DSM-IV [psychological classifications of disorders] marijuana abuse or dependence significantly increased between 1991-1992 and 2001-2002, with the greatest increases observed among young black men and women and young Hispanic men.

Further, marijuana use disorders among marijuana users significantly increased in the absence of increased frequency and quantity of marijuana use, suggesting that the concomitant increase in potency of delta-9-THC [one of the active ingredients in marijuana] may have contributed to the rising rates...

[M]arijuana abuse or dependence increased among marijuana users by 18% from 30.2% in 1991-1992 to 35.6% in 2001-2002...

The potency of delta-9-THC in confiscated marijuana from police seizure increased by 66% from 3.08% in 1992 to 5.11% in 2002...

Moreover, there was no systematic change in the frequency of marijuana use between 1991-1992 and 2001-2001...

Increasing rates of marijuana use disorders among marijuana users in the absence of increased quantity and frequency of use strengthens the argument that the increasing rates may be attributable, in part, to increased potency of marijuana."
May 2004 - Journal of the American Medical Association 

Not Clearly Pro or Con

"Results: With the exception of higher drug use in San Francisco, we found strong similarities across both cities. We found no evidence to support claims that criminalization reduces use or that decriminalization increases use.

Conclusions: Drug policies may have less impact on cannabis use than is currently thought."
May 2004 - American Journal of Public Health 

Not Clearly Pro or Con

Diane Prentiss, MA, MPH, et al., wrote the following in their article titled "Patterns of Marijuana Use Among Patients with HIV/AIDS Followed in a Public Health Care Setting," published in the Jan. 2004 issue of Journal of Acquired Immune Deficiency Syndromes (JAIDS):

"Objectives: To examine prevalence and patterns of smoked marijuana and perceived benefit and to assess demographic and clinical factors associated with marijuana use among HIV patients in a public health care setting...

Results: Overall prevalence of smoked marijuana in the previous month was 23%. Reported benefits included relief of anxiety and/or depression (57%), improved appetite (53%), increased pleasure (33%), and relief of pain (28%). Recent use of marijuana was positively associated with severe nausea and recent use of alcohol and negatively associated with being Latino.

Conclusions: The findings suggest that providers be advised to assess routinely and better understand patients' indications for self-administration of cannabis. Given the estimated prevalence, more formal characterization of the patterns and impact of cannabis use to alleviate HIV-associated symptoms is warranted. Clinical trials of smoked and noncombustible marijuana are needed to determine the role of cannabinoids as a class of agents with potential to improve quality of life and health care outcomes among patients with HIV/AIDS."
Jan. 2004 - Journal of Acquired Immune Deficiency Syndromes 

John P. Zajicek, PhD, Professor of Clinical Neuroscience at the Neurology Research and Clinical Trials Unit of the Peninsula Medical School at the University of Plymouth, et al., wrote the following in a Nov.2003 article titled "Cannabinoids for Treatment of Spasticity and Other Symptoms Related to Multiple Sclerosis (CAMS study): Multicentre Randomised Placebo-controlled Trial" in the journal Lancet:

"Background: Multiple sclerosis is associated with muscle stiffness, spasms, pain, and tremor. Much anecdotal evidence suggests that cannabinoids could help these symptoms. Our aim was to test the notion that cannabinoids have a beneficial effect on spasticity and other symptoms related to multiple sclerosis...  

Interpretation: Treatment with cannabinoids did not have a beneficial effect on spasticity when assessed with the Ashworth scale. However, though there was a degree of unmasking among the patients in the active treatment groups, objective improvement in mobility and patients’ opinion of an improvement in pain suggest cannabinoids might be clinically useful."
Nov. 2003 - John P. Zajicek, PhD 

Not Clearly Pro or Con

An Oct. 2003 article in Nature Reviews - Cancer, "Cannabinoids: Potential Anticancer Agents," by Manuel Guzman, PhD, reported:

"Cannabinoids -- the active components of Cannabis sativaand their derivatives -- exert palliative effects in cancer patients by preventing nausea, vomiting and pain and by stimulating appetite.

In addition, these compounds have been shown to inhibit the growth of tumour cells in culture and animal models by modulating key cell-signaling pathways.

Cannabinoids are usually well tolerated, and do not produce the generalized toxic effects of conventional chemotherapies."
Oct. 2003 - Nature Reviews - Cancer 

Donald Abrams, MD, Professor of Clinical Medicine at the University of California, San Francisco, et al., wrote the following in their article "Short-term Effects of Cannabinoids in Patients with HIV-1 Infection: A Randomized, Placebo-controlled Clinical Trial," (250 KB) published Aug. 2003 in the journal Annals of Internal Medicine:

"Conclusions: Smoked and oral cannabinoids [marijuana] did not seem to be unsafe in people with HIV infection with respect to HIV RNA levels, CD4 and CD8 cell counts, or protease inhibitor levels over a 21-day treatment."

The accompanying "Summaries For Patients" (35 KB) provided by the journal stated:

"Patients receiving cannabinoids [smoked marijuana and marijuana pills] had improved immune function compared with those receiving placebo. They also gained about 4 pounds more on average than those patients receiving placebo."
Aug. 2003 - Donald Abrams, MD 

Mark A. Ware, MSc, Director of Research at the Magill University Health Centre (MUHC) Pain Clinic in Canada, et al., wrote the following in a Mar. 2003 article titled "Cannabis Use for Chronic Non-Cancer Pain: Results of a Prospective Survey" in the journal Pain:

"There has been a surge in interest in medicinal cannabis in Canada. We conducted a questionnaire survey to determine the current prevalence of medicinal cannabis use among patients with chronic non-cancer pain, to estimate the dose size and frequency of cannabis use, and to describe the main symptoms for which relief was being sought...

Of the 32 subjects who used cannabis for pain, 17 (53%) used four puffs or less at each dosing interval, eight (25%) smoked a whole cannabis cigarette (joint) and four (12%) smoked more than one joint. Seven (22%) of these subjects used cannabis more than once daily, five (16%) used it daily, eight (25%) used it weekly and nine (28%) used it rarely. Pain, sleep and mood were most frequently reported as improving with cannabis use, and 'high' and dry mouth were the most commonly reported side effects. We conclude that cannabis use is prevalent among the chronic non-cancer pain population, for a wide range of symptoms, with considerable variability in the amounts used."
Mar. 2003 - Mark A. Ware, MSc 

Pro

In a Feb. 2003 article published in the British Journal of Psychiatry (BJP) titled "Adolescent Precursors of Cannabis Dependence: Findings from the Victorian Adolescent Health Cohort," which studied students in Australia from 1992 through 1998 (when they were 20-21 years old), researchers noted the following:

"Results Of 1,601 young adults, 115 met criteria for cannabis dependence. Male gender, regular cannabis use and persistent cigarette smoking independently predicted cannabis dependence. Neither smoking severity nor persistent psychiatric morbidity independently predicted dependence. Regular cannabis use increased risk only in the absence of persistent problematic alcohol use.

Conclusions Weekly cannabis use marks a threshold for increased risk of later dependence, with selection of cannabis in preference to alcohol possibly indicating an early addiction process."
Feb. 2003 - British Journal of Psychiatry 

A study of 311 young adult twin pairs conducted by Michael T. Lynskey, PhD published Jan. 2003 in the Journal of the American Medical Association (JAMA) reported:

"Results: Individuals who used cannabis by age 17 years had odds of other drug use, alcohol dependence, and drug abuse/dependence that were 2.1 to 5.2 times higher than those of their co-twin, who did not use cannabis before age 17 years...

In particular, early access to and use of cannabis may reduce perceived barriers against the use of other illegal drugs and provide access to these drugs."
Jan. 2003 - Journal of the American Medical Association 

Not Clearly Pro or Con

Stanley Zammit, PhD, Clinical Lecturer in the Department of Psychological Medicine at Cardiff University, and Peter Allebeck, MD, Professor of Social Medicine in the Department of Public Health Sciences at the Karolinska Institutet, wrote the following in their Nov. 23, 2002 article published in the British Medical Journal (BMJ):

"Cannabis was associated with an increased risk of developing schizophrenia in a dose dependent fashion both for subjects who had ever used cannabis, and for subjects who had used only cannabis and no other drugs.

Conclusions: Cannabis use is associated with an increased risk of developing schizophrenia, consistent with a causal relation. This association is not explained by use of other psychoactive drugs or personality traits relating to social integration."
Nov. 23, 2002 - Stanley Zammit, PhD  Peter Allebeck, MD

Con

A Sep. 2002 article in the journal Addiction, "Cannabis Use and Psychosocial Adjustment in Adolescence and Young Adulthood," stated:

"Cannabis use, and particularly regular or heavy use, was associated with increased rates of a range of adjustment problems in adolescence / young adulthood -- other illicit drug use, crime, depression and suicidal behaviours -- with these adverse effects being most evident for schoolaged regular users.

The findings reinforce public health concerns about minimizing the use of cannabis among school-aged populations."
Sep. 2002 - Addiction 

Ethan Russo, MD, Senior Medical Advisor at the Cannabinoid Research Institute, et al., stated in his study of four of the remaining seven legal Medical Marijuana patients, titled "Chronic Cannabis Use in the Compassionate Investigational New Drug Program: An Examination of Benefits and Adverse Effects of Legal Clinical Cannabis,"  (376 KB)  and published in the Jan. 2002 edition of the Journal of Cannabis Therapeutics (JCT):

"The aim of this study is to examine the overall health status of 4 of the 7 surviving patients in the [Compassionate IND] program. This project provides the first opportunity to scrutinize the long-term effects of cannabis on patients who have used a known dosage of a standardized, heat-sterilized quality-controlled supply of low-grade marijuana for 11 to 27 years.

Results demonstrate clinical effectiveness in these patients in treating glaucoma, chronic musculoskeletal pain, spasm and nausea, and spasticity of multiple sclerosis. All 4 patients are stable with respect to their chronic conditions, and are taking many fewer standard pharmaceuticals than previously.

Mild changes in pulmonary function were observed in 2 patients, while no functionally significant attributable sequelae were noted in any other physiological system examined in the study, which included: MRI scans of the brain, pulmonary function tests, chest X-ray, neuropsychological tests, hormone and immunological assays, electroencephalography, P300 testing, history, and neurological clinical examination.

These results would support the provision of clinical cannabis to a greater number of patients in need. We believe that cannabis can be a safe and effective medicine with various suggested improvements in the existing Compassionate IND program."
Jan. 2002 - Ethan Russo, MD

"Participants (N=1,920) in the 1980 Baltimore Epidemiologic Catchment Area (ECA) study who were reassessed between 1994 and 1996 as part of a follow-up study...

RESULTS: In participants with no baseline depressive symptoms, those with a diagnosis of cannabis abuse at baseline were four times more likely than those with no cannabis abuse diagnosis to have depressive symptoms at the follow-up assessment... In particular, these participants were more likely to have experienced suicidal ideation and anhedonia [inability to experience pleasure in normally pleasurable acts] during the follow-up period. 
Dec. 2001 - Gregory Bovasso, PhD 

Con

Lester Grinspoon, MD, Professor of Psychiatry at the Harvard Medical School, wrote in an article published in Nov. 2001 in the International Journal of Drug Policy:

"The cannabinoids in whole marijuana can be separated from the burnt plant products by devices already being perfected that will be inexpensive when manufactured in large numbers.

Inhalation is a highly effective means of delivery, and faster means will not be available for analogs (except in a few situations such as parenteral injection in an unconscious patient or one with pulmonary impairment). Furthermore, any new analog will have to have an acceptable therapeutic ratio.

The therapeutic ratio of marijuana is not known because it has never caused an overdose death, but it is estimated on the basis of extrapolation from animal data to be 20,000 to 40,000. The therapeutic ratio of a new analog is unlikely to be higher than that; in fact, it may be less safe because it will be physically possible to ingest more."
Nov. 2001 - Lester Grinspoon, MD 

Pro

In a study of "Marijuana Abstinence Effects in Marijuana Smokers Maintained in Their Home Environment," conducted through the University of Vermont, Burlington and the U.S. Air Force, Biomedical Science Corps, and published in the Oct. 2001 issue of the Archives of General Psychiatry (AGP), researchers concluded:

"This study validated several specific effects of marijuana abstinence in heavy marijuana users, and showed they were reliable and clinically significant.

These withdrawal effects appear similar in type and magnitude to those observed in studies of nicotine withdrawal."

Researchers additionally noted the following specifics regarding "withdrawal discomfort," which they stated "increased significantly during the abstinence phases and returned to baseline" when marijuana smoking resumed:

"Craving for marijuana, decreased appetite, sleep difficulty, and weight loss reliably changed across the smoking and abstinence phases. Aggression, anger, irritability, restlessness, and strange dreams increased significantly during one abstinence phase, but not the other."
Oct. 2001 - Archives of General Psychiatry 

Not Clearly Pro or Con

Anna H. Soderpalm, PhD, Post-doctoral Fellow in the Department of Psychiatry at the University of Chicago, et al., wrote in a July 2001 article titled "Antiemetic Efficacy of Smoked Marijuana: Subjective and Behavioral Effects on Nausea Induced by Syrup of Ipecac" in the journal Pharmacology, Biochemistry and Behavior:

"Although the public debate about the legalization of marijuana has continued for as long as 25 years, few controlled studies have been conducted to assess its potential medical benefits. The present study examined the antiemetic effect of smoked marijuana cigarettes (8.4 and 16.9 mg Delta(9)-tetrahydrocannabinol [THC]) compared to a highly potent antiemetic drug, ondansetron (8 mg) in 13 healthy volunteers. Nausea and emesis were induced by syrup of ipecac.

Marijuana significantly reduced ratings of 'queasiness' and slightly reduced the incidence of vomiting compared to placebo. Ondansetron completely eliminated the emetic effects of ipecac. These findings support and extend previous results, indicating that smoked marijuana reduces feelings of nausea and also reduces emesis in this model. However, its effects are very modest relative to ondansetron, and the psychoactive effects of marijuana are likely to limit its clinical usefulness in the general population."
July 2001 - Anna H. Soderpalm, PhD 

Pro

Donald P. Tashkin, MD, Director of the Pulmonary Function Laboratories at UCLA, in his article "Effects of Smoked Marijuana on the Lung and Its Immune Defenses: Implications for Medicinal Use in HIV-Infected Patients" published in the Journal of Cannabis Therapeutics (JCT), stated:

"Frequent marijuana use can cause airway injury, lung inflammation and impaired pulmonary defense against infection. The major potential pulmonary consequences of habitual marijuana use of particular relevance to patients with AIDS is superimposed pulmonary infection, which could be life threatening in the seriously immonocompromised patient.

In view of the immonosuppressive effect of THC, the possibility that regular marijuana use could enhance progression of HIV infection itself needs to be considered, although this possibility remains unexplored to date."
June 2001 - Donald P. Tashkin, MD

Con

Guy A. Cabral, PhD, in his article "Marijuana and Cannabinoids: Effects on Infections, Immunity, and AIDS"; published in the Journal of Cannabis Therapeutics (JCT), stated:

"The cumulative data obtained through cell culture studies using various immune cell populations extracted from animals or humans, together with those obtained using animal models of infection, are consistent with the proposition that marijuana and cannabinoids alter immune cell function and can exert deleterious effects on resistance to infection in humans....

However, few controlled longitudinal epidemiological and immunological studies have been undertaken to correlate the immunosuppressive effects of marijuana smoke or cannabinoids on the incidence of infections or viral disease in humans.

Clearly, additional investigation to resolve the long-term immunological consequences of cannabinoid and marijuana use as they relate to resistance to infections in humans is warranted."
June 2001 - Journal of Cannabis Therapeutics

"[M]olecules found naturally in the body, as well as in cannabis -- stimulate appetite."
Apr. 2001 - Nature 

Researchers from GW Pharmaceuticals in the UK wrote in a 2001 article published in the Journal of Cannabis Therapeutics (JCT):

"In practice it has been found that extracts of cannabis [processed whole plant compounds] provide greater relief of pain than the equivalent amount of cannabinoid given as a single chemical entity [such as Marinol]....

Some patients with multiple sclerosis who smoke cannabis [marijuana] report relief of spasm and pain after the second or third puff of a cannabis cigarette. This implies very rapid transit to, and absorption into the central nervous system. The time involved is seconds rather than minutes."
2001 -  Journal of Cannabis Therapeutics 

"Citizens who live under decriminalization laws consume marijuana at rates less than or comparable to those who live in regions where the possession of marijuana remains a criminal offense."
2000 - Journal of Public Health Policy 

Mahmoud A. ElSohly, PhD, Research Professor at the Research Institute of Pharmaceutical Sciences at the University of Mississippi, in the Journal of Forensic Sciences article titled "Potency Trends of Delta-9-THC and Other Cannabinoids in Confiscated Marijuana from 1980-1997" wrote:

"The potency (concentration of D9-THC) of marijuana samples rose from less than 1.5% in 1980 to approximately 3.3% in 1983 and 1984, then fluctuated around 3% till 1992. Since 1992, the potency of confiscated marijuana samples has continuously risen, going from 3.1% in 1992 to 4.2% in 1997. The average concentration of D9-THC in all cannabis samples showed a gradual rise from 3% in 1991 to 4.47% in 1997.

Hashish and hash oil, on the other hand, showed no specific potency trends. Other major cannabinoids [cannabidiol (CBD), cannabinol (CBN), and cannabichromene (CBC)] showed no significant change in their concentration over the years."
2000 - Mahmoud A. ElSohly, PhD 

A study published in the June 1999 American Journal of Respiratory Cell and Molecular Biology (JRCMB), stated:

"Marijuana (MJ) smoking produces inflammation, edema, and cell injury in the tracheobronchial080 mucosa of smokers and may be a risk factor for lung cancer....

We conclude that MJ [marijuana] smoke containing Delta-9-THC is a potent source of cellular oxidative stress that could contribute significantly to cell injury and dysfunction in the lungs of smokers."
June 1999 - American Journal of Respiratory Cell and Molecular Biology 

Con

"High densities of cannabinoid receptors were found in the basal ganglia and hippocampus, indicating a putative functional role of cannabinoids in movement and behaviour. Anecdotal reports suggested beneficial effects of marijuana in Tourette's syndrome (TS).

We therefore interviewed 64 TS patients with regard to use of marijuana and its influence on TS symptomatology. Of 17 patients (27%) who reported prior use of marijuana, 14 subjects (82%) experienced a reduction or complete remission of motor and vocal tics and an amelioration of premonitory urges and obsessive-compulsive symptoms.

Our results provide more evidence that marijuana improves tics and behavioural disorders in TS. It can be speculated that cannabinoids might act through specific receptors, and that the cannabinoid system might play a major role in TS pathology."
Dec. 1998 - Acta Psychiatrica Scandinavica 

Pro

Lester Grinspoon, MD, Professor of Psychiatry at the Harvard Medical School, et al., wrote in an Apr.-June 1998 article titled "The Use of Cannabis as a Mood Stabilizer in Bipolar Disorder: Anecdotal Evidence and the Need for Clinical Research" in the Journal of Psychoactive Drugs:

"The authors present case histories indicating that a number of patients find cannabis (marihuana) useful in the treatment of their bipolar disorder. Some used it to treat mania, depression, or both. They stated that it was more effective than conventional drugs, or helped relieve the side effects of those drugs. One woman found that cannabis curbed her manic rages; she and her husband have worked to make it legally available as a medicine. Others described the use of cannabis as a supplement to lithium (allowing reduced consumption) or for relief of lithium's side effects. Another case illustrates the fact that medical cannabis users are in danger of arrest, especially when children are encouraged to inform on parents by some drug prevention programs.

An analogy is drawn between the status of cannabis today and that of lithium in the early 1950s, when its effect on mania had been discovered but there were no controlled studies. In the case of cannabis, the law has made such studies almost impossible, and the only available evidence is anecdotal. The potential for cannabis as a treatment for bipolar disorder unfortunately can not be fully explored in the present social circumstances."
Apr.-June 1998 - Lester Grinspoon, MD 

Pro

Richard H. Schwartz, MD, Clinical Professor of Pediatrics at Georgetown University, Eric A. Voth, MD, Chairman of the Institute on Global Drug Policy, et al., wrote the following in their Feb. 1997 article titled "Marijuana to Prevent Nausea and Vomiting in Cancer Patients: A Survey of Clinical Oncologists" in the Southern Medical Journal:

"Marijuana, if rescheduled by the Drug Enforcement Agency, would be the only Food and Drug Administration (FDA)-approved drug to be administered by smoking. American physicians need timely, factual information about probable usage patterns and potential adverse effects of medical marijuana, and a factual complete review of the literature on the subject.

We mailed a survey to 1,500 American clinical oncologists. Of particular interest was whether and how often in the past 24 months these physicians recommended smoked marijuana, synthetic tetrahydrocannabinol, or 5-HT3 (serotonin) antagonists (ondansetron [Zofran], granisetron [Kytril]) for their patients. We also inquired whether and how often the oncologists would prescribe marijuana in the form of cigarettes, were it to be FDA-approved. Completed surveys were received from 1,122 (75%) of the oncologists.

The percentages of oncologists who prescribed or recommended selected antiemetics more than five times between 1992 and 1994 were 98% for 5-HT, antagonists, 6% for dronabinol (Marinol), and 1% for smoked marijuana. We also found that 332 (30%) of the oncologist-respondents to this nationwide survey supported rescheduling of marijuana for medical purposes; however, two thirds (67%) of the 332 respondents who were in favor of rescheduling estimated that they would write less than one prescription per month for marijuana cigarettes. A comprehensive literature review failed to provide persuasive evidence to recommend marijuana as a needed antiemetic medicine."
Feb. 1997 - Richard H. Schwartz, MD  Eric Voth, MD 

Con

Paul F. Consroe, PhD, Professor Emeritus in the Department of Pharmacology and Toxicology at the University of Arizona, et al., wrote in a 1997 article titled "The Perceived Effects of Smoked Cannabis on Patients with Multiple Sclerosis" in the journal European Neurology:

"Fifty-three UK and 59 USA people with multiple sclerosis (MS) answered anonymously the first questionnaire on cannabis use and MS. From 97 to 30% of the subjects reported cannabis improved (in descending rank order): spasticity, chronic pain of extremities, acute paroxysmal phenomenon, tremor, emotional dysfunction, anorexia/weight loss, fatigue states, double vision, sexual dysfunction, bowel and bladder dysfunctions, vision dimness, dysfunctions of walking and balance, and memory loss.

The MS subjects surveyed have specific therapeutic reasons for smoking cannabis. The survey findings will aid in the design of a clinical trial of cannabis or cannabinoid administration to MS patients or to other patients with similar signs or symptoms."
1997 - Paul F. Consroe, PhD 

Pro

Researcher H. Thomas, wrote the following in his article "Psychiatric Symptoms in Cannabis Users" published in the Nov. 1993 edition of the British Journal of Psychiatry (BJP):

"Cannabis use can lead to a range of short-lived symptoms such as depersonalisation, de-realisation, a feeling of loss of control, fear of dying, irrational panic and paranoid ideas...

The evidence that cannabis has a causative role in chronic psychotic or affective disorders is not convincing, although the drug may modify the course of an already established illness."
Nov. 1993 -  British Journal of Psychiatry 

Not Clearly Pro or Con

Rick Doblin, PhD, President of the Multidisciplinary Association for Psychedelic Studies (MAPS), and Mark A. R. Kleiman, PhD, Professor of Public Policy at the UCLA School of Public Affairs, wrote in a July 1991 article titled "Marijuana as Antiemetic Medicine: A Survey of Oncologists' Experiences and Attitudes" in the American Journal of Clinical Oncology:

"A random-sample, anonymous survey of the members of the American Society of Clinical Oncology (ASCO) was conducted in spring 1990 measuring the attitudes and experiences of American oncologists concerning the antiemetic use of marijuana in cancer chemotherapy patients. The survey was mailed to about one third (N = 2,430) of all United States-based ASCO members and yielded a response rate of 43% (1,035).

More than 44% of the respondents report recommending the (illegal) use of marijuana for the control of emesis to at least one cancer chemotherapy patient. Almost one half (48%) would prescribe marijuana to some of their patients if it were legal. As a group, respondents considered smoked marijuana to be somewhat more effective than the legally available oral synthetic dronabinol ([THC] Marinol; Unimed, Somerville, NJ) and roughly as safe. Of the respondents who expressed an opinion, a majority (54%) thought marijuana should be available by prescription.

These results bear on the question of whether marijuana has a "currently accepted medical use," at issue in an ongoing administrative and legal dispute concerning whether marijuana in smoked form should be available by prescription along with synthetic THC in oral form. This survey demonstrates that oncologists' experience with the medical use of marijuana is more extensive, and their opinions of it are more favorable, than the regulatory authorities appear to have believed."
July 1991 - Rick Doblin, PhD  Mark A. R. Kleiman, PhD

Pro

The Oct. 13, 2005 article "Cannabinoids Promote Embryonic and Adult Hippocampus Neurogenesis and Produce Anxiolytic- and Antidepressant-like Effects" (1.5 MB) by Xia Zhang et al. from the peer-reviewed Journal of Clinical Investigation stated:

"We show that 1 month after chronic HU210 [high-potency cannabinoid] treatment, rats display increased newborn neurons [brain cell growth] in the hippocampal dentate gyrus [a portion of the brain] and significantly reduced measures of anxiety- and depression-like behavior.

Thus, cannabinoids appear to be the only illicit drug whose capacity to produce increased hippocampal newborn neurons is positively correlated with its anxiolytic- and antidepressant-like effects."
Oct. 2005 - Journal of Clinical Investigation 

"Accelerated osteoclastic bone resorption has a central role in the pathogenesis of osteoporosis and other bone diseases. Identifying the molecular pathways that regulate osteoclast activity provides a key to understanding the causes of these diseases and to the development of new treatments.

Here we show that mice with inactivation of cannabinoid type 1 (CB1) receptors have increased bone mass and are protected from ovariectomy-induced bone loss.

Pharmacological antagonists of CB1 and CB2 receptors prevented ovariectomy-induced bone loss in vivo and caused osteoclast inhibition in vitro by promoting osteoclast apoptosis and inhibiting production of several osteoclast survival factors.

These studies show that the CB1 receptor has a role in the regulation of bone mass and ovariectomy-induced bone loss and that CB1- and CB2-selective cannabinoid receptor antagonists are a new class of osteoclast inhibitors that may be of value in the treatment of osteoporosis and other bone diseases."
May 2005 - Nature Medicine 

"Gliomas, in particular glioblastoma multiforme or grade IV astrocytoma, are the most frequent class of malignant primary brain tumours and one of the most aggressive forms of cancer. Current therapeutic strategies for the treatment of glioblastoma multiforme are usually ineffective or just palliative.

During the last few years, several studies have shown that cannabinoids — the active components of the plant Cannabis sativa and their derivatives — slow the growth of different types of tumours, including gliomas, in laboratory animals.

Cannabinoids induce apoptosis of glioma cells in culture via sustained ceramide accumulation, extracellular signal-regulated kinase activation and Akt inhibition. In addition, cannabinoid treatment inhibits angiogenesis of gliomas in vivo....

Remarkably, cannabinoids kill glioma cells selectively and can protect non-transformed glial cells from death. These and other findings reviewed here might set the basis for a potential use of cannabinoids in the management of gliomas."
Sep. 2004 - Neuropharmacology