Mood disorders and substance use disorders commonly occur together, but few long-term studies have questioned whether specific subtypes within these disorders are more likely to coexist. In a study published in the January issue of the journal Archives of General Psychiatry, researchers interviewed subjects over a period of 20 years in order to discover connections between mood disorders and alcohol, cannabis, and benzodiazephine abuse and dependence. They found a strong association between bipolar disorder as well as sub-threshold mania and subsequent use of all the substances included in the study.
The study, which was conducted in Switzerland and led by Dr. Kathleen Merikangas of the NIMH Mood and Anxiety Disorders Program, included 591 subjects, all of whom were around 20 years old initially. They were screened for psychiatric disorders and interviewed six times over the course of 20 years beginning in 1978. By 1993, 9.7% of the subjects had developed major depressive disorder, and although no subjects had developed the classic symptoms of bipolar disorder, 4.4% had developed bipolar II disorder, a subtype involved alternating periods of depression and mild mania. In addition, 23.5% experienced manic symptoms that did not meet the criteria for bipolar disorder. By 1999, 17.9% of the subjects abused or were dependent upon alcohol, while 8% had cannabis abuse or dependence and 3.4% had benzodiazepine abuse or dependence. After analyzing the data, the researchers found a statistically significant correlation between depression and benzodiazepine abuse/dependence. Bipolar II disorder, however, correlated to both alcohol and benzodiazepine abuse/dependence, while manic symptoms showed a significant correlation to alcohol, benzodiazepine, and cannabis abuse/dependence.
Much research has focused on, and found evidence for, the connection between mood disorders and substance abuse, especially regarding the relationship between alcohol and depression. This study indicates that mania, which correlated to all three substances studied, is also a significant risk factor for substance abuse, even if the manic periods experienced are not diagnostic of bipolar disorder. The study did not look at other factors that may have been responsible for this connection, including personality traits like impulsivity or the possibility that individuals were self-medicating, and future studies investigating these potential causes may give us a clearer picture of the relationship between substance use and other psychiatric disorder.
Is important for individuals with both substance use disorders and mood disorders to address both problems, and this study indicates that early detection and treatment of bipolar disorder and sub-threshold mania could help individuals prevent future substance abuse problems. With a better understanding of why these connections exist, we will be better able to treat individuals affected by them, and continued research is necessary to further illuminate the ways in which mood disorders and substance abuse influence each other.
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