1. In most situations, CUD in probands and families began before subtypes of mood disorders.

2. Increased risk of Cannabis use disorder (CUD) among family members of probands with Bipolar Disorder-II suggests that CUD and BP-II may have a similar underlying disease.

Evidence Rating Level: 2 (Good)

The most widely used illegal substance in the United States is cannabis.is the most prevalent substance use disorder, affecting 4.8 million people in the United States in 2019.  Previous literature has identified a link between CUD and other psychiatric comorbidities, such as depression and bipolar disorder. However, the stability of these conclusions has been called into question by the inconsistency seen across different studies. As such, this study aimed to further elucidate potential mechanisms underlying the relationship between CUD and mood disorders.

In this cross-sectional controlled family study conducted in Washington, DC, the United States, semi-structured diagnostic interviews and family history records were used to evaluate lifetime DSM-IV disorders in relatives and probands. With additional factors taken into account, mixed-effects measures were used to assess the familial aggregation and coaggregation of CUD with mood disorders. 586 adult probands (55 with CUD, 186 with bipolar disorder) and 698 first-degree relatives (68 with CUD, 91 with bipolar disorder) who were proficient in English were included in the study. The primary outcome assessed for lifetime CUD in first-degree relatives.

Study results supported a familial clustering of CUD. CUD amongst probands was associated with CUD in relatives. Furthermore, bipolar disorder II (BP-II) in probands was associated with an increased risk for CUD amongst relatives. Interestingly, bipolar disorder I and major depressive disorder in probands were not associated with CUD amongst relatives. Finally, amongst relatives, CUD was associated with mean age, major depressive disorder, and BP-II. However, this study was limited by not having the possibility of investigating potential connections between mood disorders and CUD due to the cross-sectional data. As well as a limited percentage of probands and their families fit the CUD criteria, despite the sizeable overall sample size. Nonetheless, These findings point to a possible role for BP-II treatments as CUD prevention.

Click to read study in: JAMA Psychiatry

Image: PD

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