Cannabis-Induced Psychosis 8/24/2017

As cannabis use increases, with easier access and recent legislation, there has been significant emerging evidence for cannabis-related risks. It is important for primary care providers to be aware of these, because a primary care office may be the place where patients present with these negative effects and educating patients about the potential risks is part of good care.

One the biggest risks of heavy cannabis use is cannabis-induced psychosis, which is defined as psychotic symptoms directly correlated to cannabis intoxication or withdrawal. It is particularly important to be able to clinically differentiate between cannabis-induced psychosis and primary psychosis because of its impact on prognosis and treatment. It is important to be able to educate patients and families in a situation with a new diagnosis of a primary psychotic disorder that cannabis use does not “cause” schizophrenia. Regular cannabis use can however unveil the diagnosis earlier than it would have otherwise presented.

Differentiating between primary psychosis and cannabis-induced psychosis can be challenging because a primary psychotic illness typically presents in the late teens and early adulthood, which is also a time when people are using cannabis. The timeline of the psychotic symptoms, the level of cannabis use, and the specific psychotic symptoms can be helpful to differentiate the disorders.

While it is not uncommon for a person with a primary psychotic disorder to use cannabis or other substances, cannabis-induced psychosis in a person without a primary psychotic disorder can occur when there is recent heavy ingestion of cannabis or sudden increase in potency of THC. A positive toxicology screen indicates use within the last month. The typical symptom pattern of cannabis-induced psychosis is pronounced mood lability and paranoia within 1 week (but as early as 24 hours) of use. If the psychotic symptoms precede cannabis use or if symptoms persist after abstinence for over 4 weeks, then there is a greater likelihood of a primary psychotic disorder.


The specific symptomatology between cannabis-induced psychosis and primary psychosis is subtly different. Cannabis-induced psychosis typically presents with more pronounced mood symptoms and less pronounced negative symptoms (amotivation, apathy, restricted affect) than primary psychosis. The positive psychotic symptoms can be different as well. Cannabis-induced psychosis often presents with visual hallucinations and paranoia, which interestingly is also how other medically-induced psychoses typically presents. In primary psychotic disorders, one often sees auditory hallucinations, delusions and disorganized thinking and behavior.

In cannabis-induced, the psychosis symptoms abate on their own when there is a greater length of time from last use. In a primary psychotic disorder, the psychotic symptoms continue or worsen until treatment is initiated. The antipsychotic medications can be useful for both types of psychoses. For a primary psychotic disorder, treatment becomes life-long, whereas for cannabis-induced psychosis, it can provide short-term relief of the psychotic symptoms. The more important treatment for cannabis-induced psychosis is psychoeducation about the effects of cannabis use and substance abuse treatment.

It is our hope that this primer is helpful for distinguishing between primary psychosis and cannabis-induced psychosis in the primary care setting.



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