The Tangled Links Between Substance Use Disorder and Psychosis
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Substance use disorder and psychosis frequently occur together: in fact, SUD is present in well over a third of all cases of psychosis among persons in high-income countries. Given the complexity of these conditions—many substances, many forms of psychosis, many kinds of patients—our understanding has a long way to go. One thing is increasingly clear, however: those who suffer from both conditions have much more serious health consequences than those dealing with just one of them.
If you’ve ever taken a statistics class, you may recall a certain golden rule: correlation does not equal causation. Birds and squirrels are both found in trees (that’s a correlation), but one creature’s presence may not be the cause of the other’s. Similarly, SUD and psychosis co-occur in many persons: study after study has shown this to be true. But does one cause the other, or do additional factors—income, environment, genetics, other health challenges—increase the likelihood of both SUD and psychosis in an individual?
The simple answer is, we don’t yet know. What we do know is that suffering from either condition makes any given person statistically more likely to suffer from the other as well—fully one-third more likely, in fact. As this article in the International Journal of Mental Health and Addiction notes, that’s a correlation far too great to be ignored.
We’re also learning more and more about how a combined diagnosis of SUD and psychosis tends to magnify suffering. “Patients with dual diagnosis of psychosis and SUD have higher rates of hospitalization, aggression, homelessness, suicidal mortality, and worse outcomes than those with a singular diagnosis,” notes the article.
Yet another topic explored here: how substance-induced psychotic episodes—by definition temporary—often evolve into psychosis that persists regardless of the presence of the substance use (“independent psychosis”). Young men and those with cannabis use disorder appear particularly at risk of this serious development.
This article is not a light read, but it’s an important one.
https://link.springer.com/article/10.1007/s11469-024-01279-z
Final note: the authors do point out a significant limitation of their study: only men were included. Whether or not this was intentional is unclear—but the authors do flag the issue for further investigation. This is especially important given other research suggesting that women suffering from both SUD and psychosis experience more serious health outcomes than men.
