Cannabis-Induced Psychosis and Long-term Implications 7/5/2018

As cannabis use increases, with easier access in the face of recent changes in legislation, there has been significant emerging evidence for cannabis-related risks. It is important for primary care providers to be aware of these, because the primary care office is can be a valuable opportunity for primary prevention frequently activity or may be the setting where negative effects are identified by the parent or the youth. While the focus of this article is on cannabis-induced psychosis which is associated with heavy use, primary care providers should also be prepared to address the multiplicity of other concerns related to cannabis (and substances) – these topics will be reviewed in future editions of the SmartCare eWeekly newsletter.

One the most troubling risks of heavy cannabis use is cannabis-induced psychosis, which is defined as psychotic symptoms directly correlated to cannabis intoxication or withdrawal. Of course, it is important to be able to clinically differentiate between cannabis-induced psychosis and primary psychosis because of its impact on prognosis and treatment. These primary psychotic disorders include schizophrenia and schizoaffective disorder. 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 peak time for cannabis use. The timeline of the psychotic symptoms, the level of cannabis use, and the specific psychotic symptoms can be helpful in differentiating between the disorders.

While it is known that there is a high co-morbidity between substance abuse and primary psychotic disorders, cannabis-induced psychosis in a person without a primary psychotic disorder can occur when there is recent heavy ingestion of cannabis or a sudden increase in potency of tetrahydrocannabinol (THC), the psychoactive ingredient of cannabis, used. Heavy use in this context is defined as using high potency cannabis multiple times per day.  Fortunately the risks of psychosis with moderate use (defined as using 1-2 times per day) or “recreational” use (using a few times per week) are lower.

An additional risk factor for development of a psychotic symptoms is that cannabis may be laced with another more potent psychoactive agent, including the synthetic variants known as spice. 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.

It is important to note that the symptomatologies of cannabis-induced psychosis and primary psychosis are subtly different. Cannabis-induced psychosis typically presents with more pronounced mood symptoms (mood lability, irritability, depression) 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 medically-induced organic psychoses typically presents. In primary psychotic disorders, the positive symptoms that are most often seen include auditory hallucinations, delusions and disorganized thinking and behavior.  In addition to a comprehensive history, part of the work up for any individual presenting with psychotic symptoms would include a toxicology screen

In cannabis-induced psychosis, the psychotic symptoms abate on their own as 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. Antipsychotic medications can be useful for both types of psychoses. For a primary psychotic disorder, treatment typically becomes life-long, whereas for cannabis-induced psychosis, it can provide short-term relief for the psychotic symptoms.

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. And there is more and more evidence that patients who first present with a substance-induced psychosis tend to be at substantial risk for future psychosis. Studies have shown that 50% of people who experience cannabis-induced psychosis go on to convert to a primary psychotic disorder.

While other substances are more likely to be abused (ex. alcohol) and others are more likely to cause acute psychotic symptoms (ex. methamphetamine), people who experience psychotic symptoms related to cannabis use are the ones who are most likely to convert to schizophrenia and schizoaffective disorder. The period right after the substance-induced psychosis confers the greatest risk for developing a primary psychotic disorder, but the risk can continue for several years after the substance-induced psychosis.

This is not to say that a person who experiences cannabis-induced psychosis will develop a primary psychotic disorder. Other confounding risk factors include using multiple substances, amount of use, frequency of use, genetic and environmental vulnerability, and pre-substance use psychotic and mood symptoms.

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



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