Stanley Zammit, PhD, MB, MA, Clinical Lecturer in Psychiatric Epidemiology at Cardiff University, and Peter Allebeck, MD, Professor in Social Medicine at the Karolinska Institutet, et al., in their article titled "Self Reported Cannabis Use As a Risk Factor for Schizophrenia in Swedish Conscripts of 1969: Historical Cohort Study," published Nov. 23, 2002 in the British Medical Journal, wrote:

“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