Common Comorbidities with Substance Use Disorders Research Report
Part 2: Co-occurring Substance Use Disorder and Physical Comorbidities

People with substance use disorders also often experience comorbid chronic physical health conditions, including chronic pain,99 cancer, and heart disease.100 The use of various substances—including alcohol, heroin, prescription stimulants, methamphetamine, and cocaine—is independently associated with increased risk for cardiovascular and heart disease.100

Chronic Pain

Chronic pain is a physical problem that has a complex relationship with substance use disorders, particularly opioid misuse and addiction.99 An estimated 10 percent of chronic pain patients misuse prescription opioids.99 Chronic pain and associated emotional distress are thought to dysregulate the brain’s stress and reward circuitry, increasing the risk for opioid use disorder.99 Opioid misuse and addiction are serious public health problems that led to more than 42,000 deaths in 2016 alone.101 High rates of opioid misuse and addiction among patients with chronic pain highlight the need for careful pre-treatment screening and education as well as ongoing monitoring for safety and effectiveness when opioid medications are used to treat pain.102,103

Tobacco Use

One of the largest drivers of physical health comorbidities is cigarette smoking. It is linked to many major health conditions and remains the leading preventable cause of premature disease and death in the United States.104 For example, the majority of lung cancer and approximately one-third of all cancer deaths are attributable to smoking.104 Smoking is known to contribute to age-related macular degeneration, diabetes, colorectal cancer, liver cancer, adverse health outcomes in cancer patients and survivors, tuberculosis, erectile dysfunction, rheumatoid arthritis, inflammation, and impaired immune function.104 Smoking is also an important comorbidity among people with other drug use disorders and contributes to their physical health problems. An estimated 77–93 percent of people in treatment for substance use disorders use tobacco.100

Mental Illness

Physical illnesses not only affect the body and daily functioning, but they can also increase the risk for mental illnesses such as depression105 and anxiety.106 Depression has a negative impact on individuals with chronic physical conditions, reducing a person’s quality of life and ability to manage their health.105,106 Comorbid mental illnesses are associated with greater functional impairments and mortality rates related to physical illnesses.105 Older people with chronic physical illnesses or impairments may feel isolated and increase substance use.100 Furthermore, as discussed in Part 1, mental illness may lead to substance use disorders and vice versa, thus, SUDs may play a role in linking mental illness and physical health.  

Treatment Adherence

In addition to the direct effects, substance use disorders can have an indirect negative impact on the management of medical conditions. For example, people with substance use disorders are less likely to adhere with their treatment plans or to take medication regularly,107,108 which worsens the course of their illnesses. In addition, substance use can diminish the effectiveness of medications for physical conditions.100,109

Infectious Disease Transmission

Substance use also increases the risk of infectious disease transmission, including HIV110 and the hepatitis C virus (HCV).111 This increased risk is related to injection drug use and increased risky sexual behaviors associated with drug use.110,111 For more information about the connection between substance use and HIV please go to Part 3 ("The Connection between Substance Use Disorders and HIV").

Implications for Health Care Delivery

Comorbid chronic physical and behavioral health conditions (mental and substance use disorders) are associated with greater functional impairment and increased health care costs. As with comorbid mental illness, integrated care is critical for addressing physical health comorbidities.112 As discussed in Part 4 ("Barriers to Comprehensive Treatment for Individuals with Co-Occurring Disorders"), recent delivery system innovation models provide incentives to shift health care towards integrated care models. Integrated care offers greater opportunities for primary care providers, physician specialists, and behavioral health specialists to work together to reduce the impact of mental and physical health comorbidities on substance use disorder, and vice versa, to improve overall health outcomes.113