While there is a high rate of comorbidity among mental illnesses in general, there is perhaps no other combination of disorders more dangerous to the individual and those around them than mental illness paired with substance use disorder (SUD). Together, these two illnesses can work in powerful combination, exacerbating the vulnerability and instability already experienced by individuals with poor mental health. Those with bipolar disorder are particularly at high risk for a comorbid diagnosis of SUD. These two disorders occur together so often that some even believe it should be common practice to screen bipolar individuals (specifically young adults) for drug use as soon as a diagnosis is made.
Why is it, then, that these two illnesses, seemingly distinct and unrelated to each other, are so often linked together? A recent article on the common prevalence of comorbidity between bipolar and substance use proposes that this phenomenon is due to one or a combination of three different reasons: genetic factors underlying aspects of both diseases occurring in the brain, overlapping neurobiological pathways in the brain, or one disorder fostering another.
It is commonly known that many mental illnesses are comorbid — a single diagnosis of any mental illness puts one at much higher risk for encountering another at some point in life. At any given point during a 12-month period, 50% of adults clinically diagnosed with a psychiatric disorder also had at least one other accompanying mental disorder. Anxiety and depression, for example, are two mental illnesses that have extremely high rates of comorbidity (upwards of 60%). Similar to the current understanding of how many other mental illnesses develop in conjunction with one another, one theory for understanding the particularly high comorbidity of bipolar and SUD is that they have similar genetic causes. Biological factors that lead to genetic vulnerability toward one disorder also predisposes the person to greater vulnerability toward another disorder.
Along this same trend, some scientists point toward overlapping neurobiological pathways in the brain as the root cause for high rates of SUD and bipolar occurring in conjunction with one another. As both mental illness and substance abuse progress, both disorders display a similar pattern. In bipolar, manic and depressive episodes become more frequent with shorter symptom-free periods as the untreated disease progresses; in substance abuse, addiction becomes more all-consuming as time goes on, causing the drug user to crave the high of the drug more frequently in the case of longer duration of drug use. The theory of overlapping pathways, then, points toward greater “sensitization” from an untreated disorder in the brain as a sort of “kindling,” or fuel, for the other disorder to track down the same destructive pathway when left untreated.
Although this theory explains some of the science of what causes co-occurring disorders, it does not capture the whole picture. Current psychological research describes the development of mental illness in terms of genetic and environmental influences. The environmental contributions to bipolar disorder and SUD can be best understood if SUD is conceptualized as resulting from the bipolar disorder. In an effort to deal with the intense ups and downs and extreme mood swings, people with untreated bipolar will sometimes resort to “self-medicating” with addictive substances such as alcohol, marijuana, or other drugs. Some people rely on these substances so heavily that they can even trigger manic or depressive episodes due to their use. Cocaine, for example, has been shown to potentially send people with mood disorders into a manic or hypomanic episode because of its effect on the body and complex neurotransmitter chemistry in the brain. The person, however, may view the drug as a way to remedy intense depressive episodes experienced from a bipolar “low,” unaware that the resulting hypomanic or manic episode can be just as harmful.
Due to these complex interaction effects from both disorders, it is generally recommended that people receive treatment for bipolar and SUD together and not separately, as was common practice up until recently. The very fact that these two illnesses are linked together so frequently reiterates the importance of understanding their combined effects. Even further, though, understanding the comorbidity and underlying causes between bipolar and SUD also empowers us with the even greater understanding that each individual and their needs are extremely unique and amazingly varied, making us more compassionate and empathetic practitioners, students, friends, and partners.
Mcgregor, S. Substance Abuse and Bipolar Disorder. Retrieved on February 18, 2018, from https://psychcentral.com/lib/substance-abuse-and-bipolar-disorder/
Quello, S. B., Brady, K. T., Sonne, S. C., Mood Disorders and Substance Use Disorder: A Complex Comorbidity. Retrieved on February 18, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851027/
Cameron, O. G. Understanding Comorbid Depression and Anxiety. Retrieved on February 18, 2018, from http://www.psychiatrictimes.com/anxiety/understanding-comorbid-depression-and-anxiety
Dual Diagnosis. Bipolar Disorder and Addiction. Retrieved on February 18, 2018, from https://www.dualdiagnosis.org/bipolar-disorder-and-addiction/