The Complex Relationship Between Substance Use Disorders and Mental Health Conditions
Authors
Media Contact
For general and media inquiries and to book our experts, please contact: pr@rstreet.org
Alcohol is sometimes referred to as a “social lubricant” because it can reduce inhibitions and lower anxiety for some individuals in social situations. People who smoke or use other nicotine products often perceive that these products help them focus or lower stress. These are just a few of the many ways people commonly use substances to address known—or unknown—psychological needs.
Substance use disorders and mental health conditions
About 58 percent of Americans over the age of 12 have used tobacco/nicotine products, alcohol, or illicit drugs in the past 30 days, but far fewer have a substance use disorder. In 2024, only about 13.8 percent of people who reported using illicit drugs in the past year had a drug use disorder, and only about 11.3 percent of people who used alcohol in the past year had alcohol use disorder.
More than one in five adults live with at least one mental health condition, and these individuals are more likely to have substance use disorders than the general population. It is estimated that 25 to 50 percent of those with mental health conditions also have a substance use disorder (i.e., co-occurring conditions). In total, about 2 percent of American adults (about 5.5 million people) fall into this category.
Exploring why conditions co-occur
There are many theories as to why substance use disorders and mental health conditions frequently co-occur. One hypothesis is shared genetic predisposition. In other words, genes that increase the likelihood of developing mental health conditions also increase the risk of developing a substance use disorder. Another theory is that similar brain regions and neurotransmitters (e.g., dopamine) are responsible for both conditions. Still others suggest that stress, trauma, and environmental risk factors can contribute to the development of both conditions.
The self-medication hypothesis is perhaps one of the most intuitive. This theory suggests that people with mental health conditions are prone to developing substance use disorders because they use substances to alleviate their psychological suffering. The hypothesis theorizes that substance use begins as a self-regulation or coping mechanism for mental health symptoms, and repeated use eventually leads to psychological and physical dependence.
Co-occurring conditions complicate treatment
Managing either a substance use disorder or a mental health condition can be challenging, but managing them together presents unique difficulties. Each condition can exacerbate the other, even if one did not directly cause the other, which can complicate diagnosis and treatment.
For example, when substance use is seen as a symptom of a mental health condition, some providers believe the substance use will self-regulate or disappear once the mental health issue is addressed. This can delay the diagnosis of —or willingness to treat—the substance use disorder. It can also be difficult to disentangle symptoms of intoxication from those of certain psychological conditions. Consequently, providers may fail to diagnose substance use disorders if they attribute symptoms to a mental health condition or vice versa.
Despite evidence supporting concurrent treatment over sequential treatment, people with co-occurring mental health and substance use disorders rarely receive treatment that addresses both. The Substance Abuse and Mental Health Services Administration reported in 2020 that just 7.8 percent of those with co-occurring conditions received such treatment. Even those who do receive care for both conditions may still find it difficult to find integrated treatment and struggle with the complexities of coordinating care among multiple providers.
Conclusion
About 5.5 million Americans live with co-occurring mental health and substance use disorders, yet fewer than 8 percent receive treatment that addresses both conditions. Many factors contribute to this treatment gap, including diagnostic challenges and clinical misperceptions. Closing the treatment gap will require systemic changes that address each barrier to accessing care. If we commit to improving access to concurrent treatment and integrated care, we will ensure the best outcomes for individuals with co-occurring conditions.