OBJECTIVE: More than half of the U.S. states have legalized medical marijuana. Emerging evidence suggests that medical marijuana legalization may increase marijuana use and cannabis use disorder (CUD). CUD is comorbid with, and exacerbates, numerous psychiatric conditions, including misuse of other substances. It is unclear if marijuana is a gateway to other drug use, if it is simply a marker of another variable or shared experiences. Thus, we aim to present a perspective of the potential impact of medical marijuana legalization on CUD, focusing on the relationship of CUD to other psychiatric disorders.

FINDINGS: Medical marijuana legalization may lead to problematic cannabis use in patients with depressive symptoms, individuals with genetic predispositions, and those with certain early life stressors or who use in order to cope. Past positive experience with marijuana use may contribute to patient desire to seek medical marijuana treatment. Despite approved indications, medical marijuana often only leads to partial relief of its intended target symptom. While recreational marijuana use increases likelihood of using other drugs and is detrimental to recovery from other substance use disorders, the relationship between medical marijuana use and polysubstance use or risk of addiction relapse is uncertain.

CONCLUSIONS AND RELEVANCE: Legalized medical marijuana use may increase rates of CUD, although further research is needed to clarify this association. Based on the literature, it is our perspective that patients with affective symptoms and those with other substance use disorders are at increased risk of developing CUD and its sequelae. Given the uncertainty surrounding how prescribed marijuana may interact with other disorders, it is paramount that clinicians make patient-specific judgments as to the risks and benefits of the treatment.