How Drug Abuse Can Weaken or Suppress the Immune System

When a person struggles with substance abuse or addiction, they may experience several side effects from chronically ingesting these substances. Long-term struggles with alcohol or drugs can lead to considerable damage to many systems in the body, especially the immune system. The immune system may be harmed directly by intoxicating substances, or the way the drug is ingested may contribute to a higher risk of infection, coupled with a lower immune response.

Even if someone who suffers from addiction does not develop more serious problems, like cognitive problems, heart disease, lung disease, or liver failure, harm done to the immune system can lead to serious, recurring, or incurable infections. Some of these infections may cause other long-term problems or lead to death.

Substance Abuse and the Immune System

Some of the addictive substances that can damage the immune system and lead to infectious diseases are described in further detail below.

  • Alcohol: Decreased liver and pancreas functioning can lead to immune system problems. Chronic alcohol abuse and pneumonia are linked. Reduced inhibitions associated with alcohol consumption can also lead to sexually transmitted infections, especially HIV or HSV-2, which can suppress the immune system and cause the body to become more susceptible to other infections.1
  • Cocaine: Snorting cocaine damages mucous membranes in the nose, throat, and lungs, which in turn can lead to upper respiratory infections or a susceptibility to these conditions. Smoking crack cocaine also damages the lungs and can reduce the immune system’s response to lung infections like bronchitis or pneumonia.2
  • Marijuana: This intoxicating drug affects several kinds of cells in the body, which can ultimately harm the immune system. Smoking marijuana reduces the body’s ability to resist infections from viruses, bacteria, fungi, and protozoa. Because of the suppressed ability of the immune system, it may also reduce the ability of an immune system to be able to destroy cancer cells.3
  • Nicotine: As with marijuana and crack cocaine, smoking cigarettes can lead to upper respiratory problems and a lowered immune system response to infections in that area.4
  • Opioids: This class of drugs includes heroin, morphine, fentanyl, opium, and prescription painkillers. While all narcotics have some effect on the immune system, injecting drugs into the veins increases the risk of viral infections like HIV and hepatitis B or C (due to sharing needles) and bacterial or fungal infections. This is especially dangerous in people whose immune systems are already compromised. Crushing and snorting narcotic drugs can also increase the risk of upper respiratory infections due to damage to the mucous membranes in the nose, throat, and upper lungs.5 Morphine and related opioids have been found to directly impact white blood cells, which can reduce the ability of the immune system to react to diseases.6

Overcome Addiction to Help the Immune System Heal

Entering a rehabilitation program to overcome addiction can help the body heal. Medical professionals can treat infections like pneumonia, STIs, or other diseases. Conditions like HSV or HIV that are incurable can also be treated, allowing the person to live for extended periods of time without further harm from the disease. Some harm done to the immune system or other body systems may be reversed when the person becomes sober, so prompt treatment is key. Call  to how treatment can help you or a loved one.



  1. Sarkar, D., Jung, M.K., & Wang, H.J. (2015). Alcohol and the immune system. Alcohol Research 37(2), 153-155.
  2. University of Illinois at Chicago. (1997). How cocaine may weaken the immune system.
  3. National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Population Health and Public Health Practice; Committee on the Health Effects of Marijuana. (2017). The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington DC: National Academies Press.
  4. Kalra, R., Singh, S.P., Pena-Philippides, J.C., Langley, R.J., Razani-Boroujerdi, S., & Sopori, M.L. (2004). Immunosuppressive and anti-inflammatory effects of nicotine administered by patch in an animal model. Clinical and Diagnostic Laboratory Immunology 11(3), 563-568.
  5. Friedman, H. Newton, C., & Klein, T.W. (2003). Microbial infections, immunomodulation, and drugs of abuse. Clinical Microbiology Review 16(2) 209-219.
  6. National Institute on Drug Abuse. (2008). Morphine-induced immunosuppression, from brain to spleen.


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