More evidence on cannabis psychosis

“Young people who use cannabis are doubling their risk of developing psychotic symptoms,” the Daily Mailhas reported. Mental health problems may also persist among continual users, the newspaper added.

The news is based on a study involving nearly 2,000 German adolescents and young adults. It found that new cannabis use almost doubled the risk of psychotic symptoms in the years after use. The study also found that these users had been free from psychotic symptoms prior to smoking cannabis. Previously, it has not been clear whether cannabis use leads to psychotic symptoms or whether young people with psychotic symptoms use cannabis to “self-medicate”.



New Study: Marijuana Causes Psychosis

February 08, 2011 CNN

Psychopharmacology (Berl). 2012 Mar 9. [Epub ahead of print]

Delayed preattentional functioning in early psychosis patients with cannabis use.


School of Psychology, University of Wollongong, Wollongong, NSW, 2522, Australia,



Cannabis use is prevalent among the early psychosis (EP) population. The event-related potentials, mismatch negativity (MMN) and P3a are reduced in EP. Cannabinoids have been shown to modulate N-methyl-D-aspartate receptors which are involved in MMN generation.


This study is the first to investigate the effects of cannabis use on MMN/P3a in EP.


EP was defined as a history of psychosis or psychotic symptoms with no progression to date to chronic schizophrenia. Twenty-two EP patients with cannabis use (EP + CANN), 22 non-cannabis-using EP patients (EP-CANN) and 21 healthy controls participated in this study. MMN/P3a was elicited using a two-tone, auditory paradigm with 8% duration deviants.


As expected, EP-CANN showed marked reductions in MMN/P3a amplitudes compared to controls. However, EP + CANN showed evidence of a different pattern of neurophysiological expression of MMN/P3a compared to non-using patients, most notably in terms of delayed frontal MMN/P3a latencies.


This study provides further evidence that MMN/P3a deficits are present during early psychosis and suggests that this biomarker may have utility in differentiating substance- from non-substance-related psychoses.

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