Substance use disorders (both alcohol and drug use disorders) comprise two major health conditions: “harmful substance use” and “dependence”. Harmful substance use is defined as a pattern of continuous, recurrent or sporadic use of a psychoactive substance that has caused clinically significant damage to a person’s physical or mental health. Dependence is defined as a disorder of regulation of psychoactive substance use arising from repeated or continuous use. The characteristic feature of dependence is a strong internal drive to use substances, which manifests itself by: (a) impaired ability to control substance use; (b) increasing priority given to substance use over other activities; and (c) persistence of use despite the occurrence of harm or negative consequences. Physiological features of dependence may also be present, including (1) increased tolerance to the effects of the substance or a need to use increasing amounts of the substance to achieve the same effect; (2) withdrawal symptoms following cessation of or reduction in the use of that substance; or (3) repeated use of the substance or pharmacologically similar substances to prevent or alleviate withdrawal symptoms.
Individuals with alcohol and other substance use disorders have a significantly higher risk for acquiring TB, TB reinfection and worse treatment outcomes (52–54). According to WHO estimations, alcohol is attributable to about 20% of deaths due to TB (55) and according to the World Drug Report (56), about 8% of people who inject drugs (PWID) have TB. Some research reports suggest even higher figures of TB prevalence among PWID, with about 17–52% testing positive on tuberculin skin testing, 60% of community-recruited PWID testing positive with interferongamma-release assays, and up to 68% of PWID with active TB having multidrug resistant TB (57). Worse TB treatment outcomes among people with substance use and substance use disorders are often due to associated HIV infection, or viral hepatitis B and/or C, but there are other factors as well, such as worse access to treatment, stigma and discrimination, delays in seeking care, poor treatment adherence (including to HIV and TB medication), worse treatment engagement and effectiveness, compromised immune response, malnutrition, and drug-drug interactions (52, 54). For potential drug-drug interactions, see WHO Guidelines for the management of physical health conditions in adults with severe mental disorders (38).
Targeting substance use (both alcohol and drugs) and substance use disorders is a key strategy to prevent and treat TB (58). There is evidence that treatment of substance use disorders (especially opioid agonists maintenance treatment) is associated with better initiation of and adherence to antiretroviral therapy (59, 60) improvements in TB treatment completion, and adherence to TB medication (61, 62). However, management of substance use and substance use disorders are rarely integrated into TB and HIV care.
Due to the high comorbidity between substance use disorders and TB, it is essential to ensure access to prevention, treatment and care for both conditions. People-centred care with adequate support should be available to people with comorbid TB and substance use disorders. Health professionals providing treatment of TB should be informed and capacitated to provide basic elements of care for people with substance use disorders, including screening, providing brief intervention, recognizing and managing acute and life-threatening substance use-related conditions, and referring for specialized care when needed. Professionals working in services for mental and substance use disorders should be vigilant about comorbid TB and know how to provide care for people with both conditions.
All health professionals providing TB treatment should be able to assess and manage life-threatening conditions related to substance use, including alcohol withdrawal (complicated and not complicated with delirium and/or seizures), drug overdose and substance intoxication. Health professionals should also be able to perform screening using standardized screening tools and linked brief interventions, such as the Alcohol Use Disorders Identification Test (AUDIT) (63) and the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST) (33). For those who have difficulties in stabilizing substance use disorders while receiving treatment for TB, coordinated referral, follow-up and consultation with specialized services for mental health and substance use disorders is needed. Understanding interventions for the treatment of substance use disorders (such as harm reduction, psychosocial and pharmacological interventions, and recovery management) will help improve coordination between services and increase the effectiveness of people-centred treatment and care for people with TB and substance use disorders.