Is marijuana usage associated with an increased incidence or earlier onset of mental illness?  This controversy has received fairly heavy exposure in the media lately.  With the spread of “legal” medical marijuana and increased availability through medical marijuana dispensaries, this issue is becoming more relevant.  Several recent studies examine this issue.

A large meta-analysis published in the Archives of General Psychiatry provided evidence for a relationship between cannabis use and earlier onset of psychotic illness.  They conclude that marijuana usage plays a causal role in the development of psychosis in some patients (1).

Research from Barcelona, Spain suggests that age at first cannabis use is related to age of emergence of psychiatric symptoms, especially related to the schizophrenic spectrum (2).

New synthetic cannabinoids are becoming increasingly prevalent.  An article in the journal Drug and Alcohol Dependency found that these synthetic substances can precipitate psychosis and should be avoided in persons with risk factors for psychosis (3).

An interesting editorial from the United Kingdom discusses marijuana usage and psychosis:

Numerous studies have shown that patients with psychosis are more likely to use illicit drugs than the general population, with cannabis being the most popular. There exists overwhelming evidence that cannabis use can contribute to the onset of schizophrenia and poor outcome in patients with established psychosis. Therefore, understanding why patients use cannabis and whether they are motivated to change their habits is important. The evidence is that patients with psychosis use cannabis for the same reasons the general population does, to ‘get high’, relax and have fun. There is little support for the ‘self-medication’ hypothesis, while the literature points more towards an ‘alleviation of dysphoria’ model. There is a lack of research reporting on whether psychotic patients are ready to change their use of cannabis, which has obvious implications for identifying which treatment strategies are likely to be effective (4).

Researchers in Norway found that excessive use of cannabis was associated with earlier onset of Bipolar Disorder, in contrast to alcohol usage, which was associated with later onset of Bipolar Disorder.  They surmised that early onset of Bipolar Disorder may increase the risk of cannabis use and that use of cannabis may trigger the onset of bipolar symptoms in vulnerable individuals (5).

Overall, it appears that usage of marijuana is common among patients with mental illness, especially among the schizophrenic spectrum.  While there is increased usage in persons with psychosis and mood disorders, marijuana also is associated with earlier onset of psychotic illness and bipolar disorder.

Every-Palmer S.

Te Korowai-Whāriki, A Capital and Coast District Health Board Service, Ratonga Rua O Porirua, Regional Forensic Service, Raiha Street, P O Box 50-233 Porirua, New Zealand.

BACKGROUND: Aroma, Spice, K2 and Dream are examples of a class of new and increasingly popular recreational drugs. Ostensibly branded “herbal incense”, they have been intentionally adulterated with synthetic cannabinoids such as JWH-018 in order to confer on them cannabimimetic psychoactive properties while circumventing drug legislation. JWH-018 is a potent cannabinoid receptor agonist. Little is known about its pharmacology and toxicology in humans. This is the first research considering the effects of JWH-018 on a psychiatric population and exploring the relationship between JWH-018 and psychotic symptoms. METHOD: This paper presents the results of semi-structured interviews regarding the use and effects of JWH-018 in 15 patients with serious mental illness in a New Zealand forensic and rehabilitative service.  RESULTS: All 15 subjects were familiar with a locally available JWH-018 containing product called “Aroma” and 86% reported having used it. They credited the product’s potent psychoactivity, legality, ready availability and non-detection in drug testing as reasons for its popularity, with most reporting it had replaced cannabis as their drug of choice. Most patients had assumed the product was “natural” and “safe”. Anxiety and psychotic symptoms were common after use, with 69% of users experiencing or exhibiting symptoms consistent with psychotic relapse after smoking JWH-018. Although psychological side effects were common, no one reported becoming physically unwell after using JWH-018. Three subjects described developing some tolerance to the product, but no one reported withdrawal symptoms.  CONCLUSION: It seems likely that JWH-018 can precipitate psychosis in vulnerable individuals. People with risk factors for psychosis should be counseled against using synthetic cannabinoids.

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4. Int J Dev Neurosci. 2010 Dec 21. [Epub ahead of print]

Why do patients with psychosis use cannabis and are they ready to change their use?

Kolliakou A, Joseph C, Ismail K, Atakan Z, Murray RM.

Department of Psychosis Studies, Institute of Psychiatry, King’s College London, United Kingdom.

Numerous studies have shown that patients with psychosis are more likely to use illicit drugs than the general population, with cannabis being the most popular. There exists overwhelming evidence that cannabis use can contribute to the onset of schizophrenia and poor outcome in patients with established psychosis. Therefore, understanding why patients use cannabis and whether they are motivated to change their habits is important. The evidence is that patients with psychosis use cannabis for the same reasons the general population does, to ‘get high’, relax and have fun. There is little support for the ‘self-medication’ hypothesis, while the literature points more towards an ‘alleviation of dysphoria’ model. There is a lack of research reporting on whether psychotic patients are ready to change their use of cannabis, which has obvious implications for identifying which treatment strategies are likely to be effective.

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5. Eur Arch Psychiatry Clin Neurosci. 2011 Jan 26. [Epub ahead of print]

Excessive cannabis use is associated with earlier age at onset in bipolar disorder.

Lagerberg TV, Sundet K, Aminoff SR, Berg AO, Ringen PA, Andreassen OA, Melle I.

Psychosis Research Unit, Department of Research and Development, Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway, t.v.lagerberg@medisin.uio.no.

The aim of the study was to investigate which factors are associated with age at onset in bipolar disorder with a specific focus on excessive alcohol and cannabis use, and the sequence of the onsets of excessive substance use and bipolar disorder. We investigated a naturalistic sample of 151 patients with bipolar I and II disorder receiving psychiatric treatment. Whether the presence of excessive substance use prior to bipolar disorder onset or the type of substance used (alcohol or cannabis) was associated with differences in age at onset was investigated using hierarchical and multiple linear regression analyses, adjusting for potential confounders. Patients with excessive alcohol use had a significantly later onset compared with patients with excessive cannabis use. Excessive general substance use prior to bipolar disorder onset was associated with a later onset. However, excessive cannabis use was associated with an earlier onset whether it preceded or followed bipolar disorder onset, also after adjusting for possible confounders. Excessive use of alcohol or other substances was not independently associated with age at onset in multivariate analyses. Alcohol use was associated with a later onset compared with cannabis use, suggesting different relationships to the onset of bipolar disorder. Lifetime use of cannabis predicted an earlier onset, independent of the sequence of onsets. This indicates that an early onset may increase the risk of cannabis use and that cannabis use may trigger bipolar disorder in vulnerable individuals.