Cannabis Use Disorder and its Relation to Affective Mood Disorders
Post by Baldomero B. Ramirez Cantu
The takeaway
Individuals diagnosed with cannabis use disorder (CUD) were found to have a higher risk of developing any type of unipolar depression and bipolar disorder, including both psychotic and non-psychotic forms.
What's the science?
Cannabis use disorder is characterized by persistent marijuana use despite adverse health and social consequences. The relationship between CUD and psychiatric disorders has long been a subject of debate. While CUD is often observed in individuals with affective mood disorders, the exact nature of this relationship remains unclear. Specifically, it raises the question: Does cannabis use disorder contribute to the development of affective mood disorders, or do pre-existing affective mood disorders increase the likelihood of CUD? This week in JAMA Psychiatry, Jefesen et al. investigate whether there is an association between cannabis use disorder and an increased risk of two types of mood disorders: psychotic and non-psychotic unipolar depression, as well as bipolar disorder.
How did they do it?
The authors utilized longitudinal data from nationwide Danish health registers to address their questions. These registers provided valuable information, including basic demographic data (such as date of birth, age, and vital status), psychiatric and substance use information, and data on parental factors. A total of 6,651,765 individuals were included and followed up over 119, 526, 786 person-years (50.3% female; 49.7% male).
The authors collected additional data on variables such as alcohol use disorder (AUD), substance use disorder (SUD), sex, country of birth, parental history of CUD, AUD, and SUD, parental affective disorders, and highest level of parental education. Information on affective mood disorders and their psychotic features was obtained from national health registries.
Individuals were included in the study on their 16th birthday or on January 1, 1995, whichever occurred later. To examine the risk of presenting affective disorders based on CUD exposure, the authors employed Cox proportional hazards regression and calculated hazard ratios (HRs). The analysis incorporated appropriate controls to account for confounding factors related to the use and abuse of other substances and the influence of other variables on hazard rate changes. In essence, Cox proportional hazards regression allowed the researchers to assess the relationship between cannabis exposure and the probability or risk of developing affective disorders, as reflected in the hazard ratios.
What did they find?
Among individuals diagnosed with cannabis use disorder (CUD), 40.7% also received a diagnosis of unipolar depression. The majority (96.1%) of these cases were classified as non-psychotic unipolar depression, while a smaller proportion was classified as psychotic unipolar depression (3.9%). After adjusting for factors such as sex, alcohol use disorder (AUD), substance use disorder (SUD), birthplace, parental CUD, SUD, AUD, and affective mood disorders, the analysis revealed that individuals with CUD had a higher risk of developing any type of unipolar depression compared to those without a record of CUD (HR 1.84). Elevated risks were also observed for both psychotic depression (HR 1.97) and nonpsychotic depression (HR 1.83).
Furthermore, the study found that 14.1% of individuals diagnosed with CUD eventually received a diagnosis of bipolar disorder. The majority (90.2%) of these cases were diagnosed with nonpsychotic bipolar disorder, while 9.8% were diagnosed with psychotic bipolar disorder. The increased risk of bipolar disorder following a CUD diagnosis was observed in both men and women. The highest risk of bipolar diagnosis occurred within the first 6 months after a CUD diagnosis, but the risk remained elevated even after 10 or more years following the diagnosis.
What's the impact?
Cannabis is one of the most prevalent psychoactive substances globally, and has witnessed legalization and regulation in numerous countries over the past few decades. Gaining a comprehensive understanding of the associated risks and impacts is crucial for informing policy decisions on cannabis regulation and educating the general population about its potential risks.