Daniel K. Hall-Flavin, MD, a consultant in the Department of Pyschiatry and Psychology at the Mayo Clinic, stated the following in the "Expert Answers" section of the Mayo Clinic website in response to the question "I'm curious about marijuana and depression. Can marijuana cause depression?" (accessed June 11, 2012):
"Some research suggests that marijuana smokers are diagnosed with depression more often than are nonsmokers — particularly regular or heavy marijuana users. However, it doesn't appear that marijuana directly causes depression. It's likely that the genetic, environmental or other factors that trigger depression also lead to using marijuana. For example, some people may use marijuana as a way to cope with depression symptoms.
There are also links between marijuana and other mental health conditions. Marijuana use may trigger schizophrenia or detachment from reality (psychosis) in certain people. There is also some evidence that adolescents who attempt suicide may be more likely to use marijuana than those who don't. As with marijuana use and depression, more research is needed to better understand these associations.
The bottom line: Marijuana use and depression accompany each other more often than you might expect by chance, but there's no clear evidence that marijuana directly causes depression."
Is Medical Marijuana an Effective Treatment for Depression, Bipolar Disorders, Anxiety, and Similar Mood Disorders?
D. Mark Anderson, PhD, Assistant Professor of Economics at Montana State University, Daniel I. Rees, PhD, Professor of Economics at the University of Colorado Denver, and Joseph J. Sabia, PhD, Assistant Professor of Economics at San Diego State University, stated the following in their Jan. 2012 study "High on Life? Medical Marijuana Laws and Suicide," published by the The Institute for the Study of Labor (IZA) in its Discussion Paper Series:
"Consistent with the hypothesis that marijuana can be an effective treatment for depression and other mood disorders, there appears to be a sharp decrease in the suicide rate of 15- through 19-year olds males in the treatment states as compared to the control states approximately two years after legalization...
Our results suggest that the legalization of medical marijuana is associated with a 5 percent decrease in the total suicide rate, an 11 percent decrease in the suicide rate of 20- through 29-year-old males, and a 9 percent decrease in the suicide rate of 30- through 39 year-old-males. Estimates for female suicide rates are generally measured with less precision and are sensitive to functional form...
The strong association between alcohol consumption and suicide related outcomes found by previous researchers... raises the possibility that medical marijuana laws reduce the risk of suicide by decreasing alcohol consumption."
Thomas F. Denson, PhD, Professor of Psychology at the California State University at Long Beach, and Mitch Earleywine, PhD, Associate Professor of Psychology at the State University of New York at Albany, wrote the following in their Apr. 2006 study titled "Decreased Depression in Marijuana Users," published in Addictive Behaviors:
"Those who consume marijuana occasionally or even daily have lower levels of depressive symptoms than those who have never tried marijuana. Specifically, weekly users had less depressed mood, more positive affect, and fewer somatic complaints than non-users. Daily users reported less depressed mood and more positive affect than non-users... Our results add to the growing body of literature on depression and marijuana and are generally consistent with a number of studies that have failed to confirm a relationship between the two after controlling for relevant variables...
The potential for medical conditions to contribute to spurious links between marijuana and greater depression requires further investigation."
George McMahon, author and medical marijuana patient in the US Federal Drug Administration's Investigational New Drug (IND) program, stated in his 2003 book Prescription Pot:
"People who have never struggled with a life threatening or disabling illness often do not comprehend how debilitating the resulting depression can be. Long days spent struggling with sickness can wear patients down, suppress their appetites and slowly destroy their wills to live. This psychological damage can result in physiological effects that may be the difference between living and dying.
The elevated mood associated with cannabis definitely affected my health in a positive manner. I was more engaged with life. I took walks and rode my bike, things I never considered doing before in my depressed state, even if I had been physically capable. I ate regular meals and I slept better at night. All of these individual factors contributed to a better overall sense of well-being."
Tod Mikuriya, MD, a former psychiatrist and medical coordinator, was quoted as stating the following in the 1997 book Marijuana Medical Handbook written by Dale Gieringer, Ed Rosenthal, and Gregory T. Carter:
"The power of cannabis to fight depression is perhaps its most important property."
Frank Lucido, MD, a private practice physician, stated in his article "Implementation of the Compassionate Use Act in a Family Medical Practice: Seven Years Clinical Experience," available on his website (accessed June 11, 2012):
"With appropriate use of medical cannabis, many of these [cannabis-using] patients have been able to reduce or eliminate the use of opiates and other pain pills, ritalin, tranquilizers, sleeping pills, anti-depressants and other psychiatric medicines, as well as to substitute the use of medical cannabis as a harm reduction measure for specific problematic or abused substances with a much more serious risk profile (including alcohol, heroin/opiates, and cocaine)."
Jay Cavanaugh, PhD, National Director for the American Alliance for Medical Cannabis, wrote in his 2003 article "Cannabis and Depression," published on the American Alliance for Medical Cannabis website:
"Numerous patients report significant improvement and stabilization with their bipolar disorder when they utilize adjunctive therapy with medical cannabis. While some mental health professionals worry about the impact of cannabis on aggravating manic states, most bipolar patients trying cannabis find they 'cycle' less often and find significant improvement in overall mood. Bipolar disorders vary tremendously in the time spent in the depressive versus manic states. Those who experience extended depressive episodes are more likely to be helped with cannabis.
Patients who use cannabis to 'relax' may be treating the anxiousness sometimes associated with depression. Cannabis aids the insomnia sometimes present in depression and can improve appetite. Better pain control with cannabis can reduce chronic pain related depression. While cannabis cannot yet be considered a primary treatment of major depression it may improve mood when used under physicians supervision and in combination with therapy and/or SSRI's."
Bill Zimmerman, PhD, former President of Americans for Medical Rights (AMR), stated in his 1998 book Is Marijuana the Right Medicine For You?:
"Some patients have found the mood altering effects of marijuana to be helpful for treating mood disorders such as anxiety, depression and bipolar (manic-depressive) illness. Using marijuana to treat mood disorders was described in medical writings in the 19th and early 20th centuries...
The mental component of the pre-menstrual syndrome (PMS) often causes psychological problems and is now technically classified as an atypical (not typical) depression. Many women report benefit from using marijuana to improve the symptoms of PMS."
Gregory E. Simon, MD, MPH, Senior Scientific Investigator in the Center for Health Studies at the Group Health Cooperative, stated the following in a Jan. 2012 column titled "Ask the Doctor Q & A," published on the Depression and Bipolar Support Alliance website:
"Using marijuana can certainly contribute to or worsen depression. Low motivation, fatigue, and withdrawal from positive activities are central features of depression and marijuana can worsen each of those problems. Some people do say that marijuana dulls anxiety or negative feelings. But it also dulls energy and motivation. And we know that activation and engagement are key parts of recovery from depression.
Marijuana can be even more troublesome for people—especially younger people—who live with bipolar disorder. In addition to worsening depression, marijuana can increase the likelihood of experiencing symptoms of psychosis—like hallucinations or paranoid ideas. In younger people who are at higher risk for bipolar disorder or schizophrenia, using marijuana increases the chances of developing a severe or disabling mental illness."
The University of Washington Alcohol and Drug Abuse Institute stated the following in an online fact sheet titled "Mental Health and Marijuana," based on information from the National Cannabis Prevention and Information Centre (acessed June 14, 2012):
"Evidence suggests that marijuana may somehow trigger schizophrenia in those who are already at risk of developing the disorder. Those with a vulnerability to develop schizophrenia, such as having a family history of the illness, should be strongly advised against using marijuana for this reason...
Marijuana may seem to help ease depression before the effects of the drug wear off; however after that, smoking marijuana may make depression worse. Those who use marijuana have been shown to have higher levels of depression and depressive symptoms than those who do not use marijuana. Although results are mixed, there is a substantial amount of evidence to suggest that marijuana use, particularly frequent or heavy use, predicts depression later in life. Young women appear to be more likely to experience this effect.
Marijuana can lead to symptoms of anxiety, such as panic, in the short-term, but there is a lack of evidence pointing to marijuana as an important risk factor for chronic anxiety disorders...
Again, if someone has a genetic vulnerability or has an existing mental health issues, marijuana should be avoided."
Karen Cameron, RNC, MSN, Correspondent for WebMD, stated in a June 14, 2004 article titled "Are Depression and Marijuana Linked?" and posted on the website WebMD:
"It is pretty well known that the psychoactive chemicals in marijuana interfere with the balancing process that antidepressants work toward.
As you may already know, depression is a biochemical illness -- an imbalance in chemicals in the brain. Those antidepressants help things become better balanced, but they can't do the job nearly as well if one is smoking marijuana.
Marijuana contributes to depression and destroys natural sleep. There really is no good reason to continue smoking it."
The National Health Service (NHS) of the United Kingdom stated in a July 15, 2011 article titled "Does Cannabis Interact with Antidepressants or Lithium?" and posted on its website:
"It is not clear how often cannabis itself can cause depression, but research suggests that this can happen. It is therefore recommended that if you are depressed, and you use cannabis regularly, you should try giving up and see if that helps.
Tachycardia (an abnormally fast heartbeat), dizziness, anxiety, drowsiness, nausea, vomiting, difficulty sleeping and confusion are all possible side effects of cannabis. These side effects can also be caused by certain antidepressants, so using cannabis at the same time can make them worse.
Both TCAs [Tricyclic antidepressants] and cannabis can cause tachycardia and hypertension. You should not smoke cannabis if you take TCAs because of these risks to your heart. Either stop using cannabis or ask your doctor for an SSRI antidepressant, which appears to be a safer choice."
The Office of National Drug Control Policy (ONDCP) stated the following in its May 2008 report titled "Teen Marijuana Use Worsens Depression: An Analysis of Recent Data Shows 'Self-Medicating' Could Actually Make Things Worse," available on the National Criminal Justice Reference Service website:
"Some teens use marijuana to relieve the symptoms of depression ('self-medicate'), wrongly believing it may alleviate these depressed feelings...
However, recent studies show that marijuana and depression are a dangerous combination. In fact, using marijuana can worsen depression and lead to more serious mental health disorders, such as schizophrenia, anxiety, and even suicide. Weekly or more frequent use of marijuana doubles a teen's risk of depression and anxiety..."
Allan N. Schwartz, PhD, Licensed Clinical Social Worker and Psychoanalyst, stated the following in a Nov. 1, 2008 article titled "Marijuana Makes It Worse: Severe Mental Illnesses," posted online at mentalhelp.net:
"I have directly witnessed the tragedy of patients going off of their medications for Bipolar Disorder, using marijuana and ending up re-hospitalized in worse shape than any time prior to the relapse. In fact, it has been my experience that many of these unfortunate patients experienced multiple relapses and were caught in an endless cycle of hospitalizations marked by periods of instability in between...
It has been my experience with the patients I knew who suffered from severe bipolar disorder and with those who fell into the Schizoaffective domain, that they were not helped by marijuana and were made much worse through its use.
Leaving aside anxiety, those who experience severe depression and who use marijuana end up feeling much more depressed, at least that is what I have witnessed."