Common Comorbidities

Learn about the common comorbidities, or primary conditions and chronic diseases, which can occur in people in medication-assisted treatment (MAT) for substance use disorders.

People with substance use disorders are at particular risk for developing one or more primary conditions or chronic diseases. When primary conditions simultaneously co-occur with substance use disorders, they are referred to as comorbidities.

HIV, AIDS, and viral hepatitis are important public health concerns for both patients and health professionals in SAMHSA-supported substance use disorder treatment programs. Medication-assisted treatment (MAT) typically involves HIV and hepatitis antibody testing at admission, or a referral for antibody testing.

The coexistence of both a mental illness and a substance use disorder is also common among people in MAT. This is referred to as having co-occurring mental and substance use disorders. People with a mental health issue are more likely to experience a substance use disorder than those not affected by a mental illness. It is important to note that combining medications used in MAT with anxiety treatment medications can be fatal. Types of anxiety treatment medications include derivatives of Benzodiazepine, such as Xanax or valium.

Viral Hepatitis in MAT

There are three major strains of hepatitis virus infection: hepatitis A, hepatitis B, and hepatitis C. People at high risk for infection can be protected by vaccination against hepatitis A and hepatitis B. Currently, there is no vaccination against hepatitis C.

Hepatitis A, a self-limiting foodborne pathogen, can induce severe liver disease in drug users already infected with another hepatitis virus. Hepatitis B virus can be spread through sexual contact, blood transfusions, or by the re-use of contaminated needles.

Injection drug use is the major source of hepatitis C infection in Western countries. The hepatitis C virus is easily transmitted among injection drug users, and hepatitis C infection is common in people seeking treatment at SAMHSA-certified opioid treatment programs (OTPs). Treatment for hepatitis B infection and/or hepatitis C infection is complex, long-term, and most effective for people who are off drugs.

According to an article by the National Institute on Drug Abuse, Viral Hepatitis — A Very Real Consequence of Substance Use – 2013, each injection drug user infected with hepatitis C virus is likely to infect about 20 others, and that this rapid transmission of the disease occurs within the first three years of initial infection.

Resources and Publications

The following resources and publications highlight the link between substance misuse and comorbid hepatitis:


Drug use is an important driver of the HIV epidemic. Nine percent of all new HIV infections occur among injection drug users, 3% of whom are men who have sex with men (MSM). At the end of 2010, 56% of people living with HIV in the United States were MSM or MSM injection drug users.

Currently, no vaccine exists to protect a person from getting HIV, and there is no cure. However, HIV prevention and reduced transmission are key goals of OTPs and other programs designed to treat substance use disorders. HIV medications can also help prevent HIV transmission and the progression of HIV to AIDS, prolonging lives.

HIV is transmitted by contact with the blood or other body fluids of an infected person. This can occur during unprotected sex or through the sharing of needles. In addition, untreated infected women can pass HIV to their infants during pregnancy, delivery, and breastfeeding. Alcohol and drug misuse can also worsen the symptoms of HIV, causing greater neuronal injury and cognitive impairment.

Alcohol and illicit drugs can contribute to unsafe sexual behavior, such as unprotected sex with multiple partners. Injection drug use with heroin can also result in HIV infection through direct virus infection from contaminated needles. People in substance use disorder treatment, which often includes HIV testing and risk-reduction counseling, have been shown to stop or decrease their drug use and related risk behaviors, including risky injection practices and unsafe sex.

The following publications and resources highlight the link between substance misuse and comorbid HIV and AIDS:

Co-Occurring Disorders in MAT

The coexistence of both a mental illness and a substance use condition is referred to as a co-occurring disorder. Co-occurring disorders may include any combination of two or more substance use disorders and mental disorders identified in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).

People with a mental health issue are more likely to experience a substance use disorder than those not affected by a mental illness. According to SAMHSA’s 2012 National Survey on Drug Use and Health (NSDUH), approximately 8.4 million adults in the United States have a co-occurring disorder.

No specific combinations of substance use disorders and mental disorders are defined uniquely as co-occurring disorders. Some of the most common mental disorders seen in MAT patients with co-occurring substance use include:

  • Anxiety and mood disorders
  • Schizophrenia
  • Bipolar disorder
  • Major depressive disorder
  • Conduct disorders
  • Post-traumatic stress disorder
  • Attention deficit hyperactivity disorder

Learn more about the most common mental disorders in the United States.

Patients being treated for mental disorders also often misuse the following types of substances:

  • Alcohol
  • Tobacco
  • Opioids
  • Stimulants
  • Marijuana
  • Hallucinogens
  • Prescription drugs

Learn more about the most common substance use disorders in the United States.

Learn about individualized assessment and treatment for co-occurring disorders.

Last Updated: 10/21/2019