What Is Comorbidity?

Understanding the Prevalence of Co-Occurring Disorders

Comorbidity refers to when an individual has one or more disorders at the same time. Co-occurring disorders are common, and as noted by the Substance Abuse and Mental Health Services Administration (SAMHSA), individuals with substance use disorders are at a higher risk of developing another condition or disease. 

It is also common for individuals to have both a mental health and substance use disorder occurring at the same time. The 2018 National Survey on Drug Use and Health noted that over 9 million adults had a co-occurring disorder.

Mental Illness and Drug Use/Substance Use Disorders

Data from the National Institute on Drug Use suggests that there are common risk factors that can contribute to both mental illness and substance use disorders making it more likely that a person experiencing one, may also experience the other. 

It also shows that mental health conditions themselves may be a risk factor for developing a substance use disorder. Studies indicate that people with mental health disorders may use alcohol or drugs as a form of “self-medication” when they cannot or do not receive the treatment they need for the underlying condition. 

Furthermore, research shows that the use of drugs or alcohol can contribute to the development of certain mental health conditions. Addiction or reliance on a substance may “change the brain in ways that make a person more likely to develop a mental illness.”

Comorbidity Around the World

According to the Australian Department of Health, as many as one in five Australians between the ages of 16 and 85 experienced a mental health disorder. Of those individuals, one in four experienced more than one mental health disorder. The two most common co-occurring disorders were affective and anxiety disorders.