Alysha Sultan, BSc, PhD student1,2
Benjamin I. Goldstein, MD, PhD, FRCPC1,2,3
1 Centre for Youth Bipolar Disorder, Sunnybrook Health Sciences Centre, Toronto, Canada.
2 Department of Pharmacology, University of Toronto, Toronto, Canada.
3 Department of Psychiatry, University of Toronto, Toronto, Canada.
Spoiler alert: the quick answer is “no”. Here’s why.
The recent legalization of cannabis in Canada have been accompanied by increased use and decreased perceptions of harm of cannabis . In addition to the episodes of depression and mania/hypomania that define bipolar disorder (BD), approximately 1 in 3 teens with BD have comorbid substance use disorders and cannabis is one of the most commonly used substances by teens with BD . Teens with BD are much more likely to use cannabis than teens in general. There are a number of potential reasons BD is linked with cannabis and other substances: risk for BD and for substance use disorders may run together in families, comprising both a genetic and environmental risk factor. Anxiety and depression symptoms are very common in BD, and teens may use cannabis with the intention of reducing those symptoms. Cannabis is an intoxicating substance, and teens with BD may be especially likely to enjoy and seek out that intoxication, whether because of thrill-seeking traits, because of increased need for pleasurable rewards, or other factors. One study asked teens with BD why they use substances: teens with BD were more likely than other teens to cite “change in mood” as the driving factor for initiation and continuation of use of substances . It appears that teens with BD describe their use of substances in ways that suggest self-medication. But is cannabis a reasonable treatment for BD?
If cannabis is to be considered a potential treatment, it is prudent to review which factors are associated with cannabis use in teens. As it turns out, there is relatively consistent evidence that cannabis use is associated with more severe, rather than less severe, psychiatric symptoms. Cannabis use among people with BD has been associated with increased symptom severity, decreased treatment response, more and longer-lasting mood episodes, more psychosis symptoms, greater risk of suicide attempts or other forms of self-harm, increased number of co-occurring problems including other substance use disorders, and anxiety disorders, and police contact/arrests [4–8] . Individuals with BD who use cannabis excessively are more likely to experience academic failure [4,9], and while they tend to engage in more social activities, they also report less life satisfaction and are less likely to be in a relationship compared to individuals who did not use cannabis . Finally, cannabis use in teens with BD is associated with low rates of treatment adherence including staying consistent with therapy as well as medications. Therefore, in addition to the biological effects of cannabis potentially interfering with the effectiveness of treatment, cannabis is also associated with reduced treatment exposure/dose, which reduces the likelihood that the medication/therapy is going to help . All of these aspects lead to a more severe course of illness.
It is important to note that most studies examining correlates of cannabis use in teens with BD have been cross-sectional observational studies, meaning we can’t draw causal conclusions from them. It could be that those same individuals with the most severe psychiatric symptoms choose to try cannabis as a self-medication approach. It could also be that someone with BD who is stable makes the decision to use some cannabis and this triggers a manic or depressive episode. We encounter individuals in each of these scenarios. In either case, there is little evidence to suggest that cannabis use is associated with reduced psychiatric symptoms and/or improved life functioning among teens with BD. A study of adults found that whereas cannabis use at a given timepoint predicted subsequent manic symptoms, the reverse was not shown (i.e. worse mood symptoms did not predict increased cannabis use).
How do we square the above data with the commonly encountered scenario of teens, sometimes corroborated by their parents, who believe that cannabis is a crucial aspect of their (self-) treatment? Anything is possible for an individual. We cannot dismiss the possibility that there may be a subset of individuals for whom cannabis could be an effective treatment. But unless and until more is known about who can potentially benefit from cannabis as a treatment, it is advisable to stick with current treatment guidelines which emphasize medications and therapies that have been rigorously studied. What about recreational cannabis use among teens with BD? It is safe to conclude that the risks of cannabis use are substantially elevated in teens with BD. As such, abstaining, or at least taking a minimalist approach (i.e. as infrequently as possible, as low a dose/amount as possible), is advisable. That said, even infrequent or minimal use of cannabis has the potential to worsen symptoms or trigger a full-fledged manic or psychotic episode in some individuals. Ultimately, teens with BD will make their own decisions about cannabis use. It is important for clinicians to convey a sincerely non-judgmental stance, while also serving as a portal to reliable information about the potential risks of cannabis use and as trusted consultants who can help teens critically evaluate the role of cannabis in their lives.
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