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The Connection Between Addiction and Disease


Medically Reviewed by Dr. Mohammed Saeed, MD.

Addiction and Disease

As a society, we continue to debate whether or not addiction should be considered a disease. The National Institute on Drug Abuse (NIDA) classifies addiction as a disease because it “disrupts the normal, healthy functioning of an organ in the body,” particularly the brain. While some view addiction as a choice, others argue that addictive behavior has been linked to specific genes, just like other diseases such as diabetes, cancers, or depression.

A genetic predisposition is not a guarantee that a person will develop an addiction. Environmental factors also influence a person’s likelihood of abusing a substance. Consider an analogy to diabetes. Children of diabetic parents may not develop diabetes, even if they inherited the gene associated with the disease. Similarly, children of non-diabetic parents could develop diabetes by eating a diet high in processed carbohydrates and sugary drinks.

Can Disease Lead to Addiction?

One of the risk factors for developing an addiction is mental illness. Depression or anxiety, for instance, can influence a person to self-medicate in order to moderate their moods. Drinking alcohol or smoking marijuana may provide temporary relief from a low mood or high stress. However, in the long term, the use of an addictive substance amplifies depression or anxiety. Over time, a cyclical pattern develops in which a person increases both their consumption of and dependence on a substance.

A person can be also afflicted with “two or more disorders or illnesses.” NIDA refers to this as “comorbidity,” also referred to as dual diagnosis and co-occurring disorders. The illnesses can occur simultaneously or sequentially. For example, there is a high correlation between mental illness and substance abuse disorder.

NIDA references studies reporting that about fifty percent of people with mental illness, including depression, anxiety, and PTSD, abuse drugs, alcohol, or both. The correlation also stands when considering individuals with mental illness: about half of them will also have a substance abuse disorder.

Can Addiction Cause Disease?

Whether or not addiction itself is considered a disease, there is no doubt that substance abuse lowers the body’s natural defenses to other diseases. Alcohol and drugs inhibit the immune system’s ability to protect against bacteria, viruses, and cancers. As a result, people afflicted with addiction are more likely to develop pneumonia, bronchitis, or other diseases. If a person’s method of use is by injection, they also risk contracting HIV or hepatitis. Additionally, risky behavior associated with drug and alcohol use, such as unprotected sex, increases the odds of contracting sexually transmitted diseases.

Below we look at more specific connections and correlations between different addictions and diseases:


The National Institute on Alcohol Abuse and Alcoholism (NIAAA) states that drinking “can take a serious toll on your health.” Whether excessive consumption takes place over a long period of time or a short period, alcohol affects the heart, liver, kidneys, and pancreas. Heavy alcohol consumption can lead to heart and cardiovascular diseases, which include arrhythmia, stroke, and high blood pressure.

The liver, which filters the blood of toxins, can become fatty and thick with heavy drinking. According to the American Liver Foundation (ALF), almost all heavy drinkers develop fatty liver disease, which is reversible if caught early and drinking stops. More severe alcohol-related liver diseases are alcoholic hepatitis and cirrhosis. ALF states that about thirty-five percent of heavy drinkers will develop alcohol-related hepatitis, which can create jaundice and other health complications. Alcohol-related cirrhosis is extremely serious and not reversible. In cirrhosis, non-living scar tissue replaces living liver cells, inhibiting the liver’s ability to perform its hundreds of physiological functions in addition to removing toxins from the body.

The kidneys also filter toxins from the body. Alcohol adversely impacts the efficiency of the organs by changing their ability to regulate fluids and electrolytes in the bloodstream. This often results in dehydration, another negative effect for the kidneys and potentially leading to high blood pressure and, if left untreated, kidney disease.

The pancreas helps control blood sugar levels by excreting insulin and glucagon. It also excretes three enzymes into the stomach to help with the digestion of fats, carbohydrates, and proteins. Over time, alcohol can create pancreatitis, a painful inflammation that interferes with the pancreas’ normal functioning.

According to the (NIAAA), here is a list of some of the cancers associated with excessive drinking:

  • Cancers of the mouth and esophagus
  • Liver Cancer
  • Breast Cancer
  • Colorectal Cancer


Research has established a clear connection between nicotine, a highly addictive substance, and lung cancer. Marijuana smokers often smoke cigarettes as well, so the correlation between lung cancer and cannabis is less clear (see below for more on marijuana and disease). Smoking is also associated with chronic obstructive pulmonary disease (COPD). COPD refers to both chronic bronchitis and emphysema. Asthma, another lung disease, can develop or worsen as a result of smoking. Cigarettes have links to strokes, heart disease, pneumonia, cataracts, and various cancers.


Cannabis is typically eaten (via edibles) or smoked. Compared to smoking cigarettes, users who smoke marijuana inhale more deeply, bringing the smoke deeper into the lung tissues and holding it in their lungs for longer, increasing their risks for respiratory infections. According to NIDA, “[r]esearchers so far haven’t found a higher risk for lung cancer in people who smoke marijuana.” However, marijuana smokers can develop other lung complications, including daily coughing and phlegm, infections, and illnesses such as bronchitis.


Depending on how cocaine is taken, the long-term health effects will vary. Snorting the powder can deteriorate the sense of smell and create nose bleeds. Smoking cocaine will impact the lungs in a similar way as cigarettes. Ingesting cocaine by mouth will lead to severe bowel problems. Short-term use affects the heart and circulatory system, which can lead to high blood pressure and other serious cardiovascular issues. The American Heart Association quotes researchers as referring to cocaine as “the perfect heart attack drug.”


Heroin has different methods of use: injection, smoking and snorting. Each of the methods has associated health and potential disease risks. If injected with a needle, users risk getting HIV or hepatitis from the needle. Additionally, with excessive injections, veins can collapse, causing other complications. Smoking heroin creates lung complications and can lead to pneumonia. Snorting the drug over time deteriorates the nasal tissues. All heroin users increase the risk of infections to the heart valves and pericardium, the thin membrane surrounding the heart. Liver and kidney disease are also common among heroin users.


Opioids like morphine, fentanyl, codeine, and oxycodone relax the body and relieve pain while also providing a sensation of euphoria and well-being. One possible serious side effect opioids can have on the body is slowing breathing to a dangerously low rate. If breathing slows too drastically, a person can suffer from hypoxia, when too little oxygen reaches the brain. Depending on the length of time, hypoxia can result in the person slipping into a coma, experiencing psychological or neurological effects, or living with permanent brain damage. When opioids are taken without a prescription, users run the risk of an adverse reaction with other medications they may be taking.


The long-term health implications of hallucinogens depend in part on the type taken. There are two classes of hallucinogens: classic and dissociative. Classic hallucinogens include LSD, psilocybin, peyote, and DMT. Over time, if abused, these drugs can create persistent psychosis and Hallucinogen Persisting Perception Disorder, commonly thought of as “flashbacks,” although this label oversimplifies the disorder. Dissociative drugs include PCP, DXM, and salvia. When overused, these hallucinogens can create speech problems, memory loss, anxiety, and depression.


Once a club drug, MDMA, also known as Molly and Ecstasy, has become more mainstream. MDMA stimulates the body’s heart rate and blood pressure, making the drug more dangerous for users with cardiovascular concerns. The drug inhibits the body’s ability to regulate internal temperature, so a user’s temperature can increase dangerously and can cause liver, kidney, or heart failure.

Disease and Addiction Often Co-occur

The connection between addiction and disease is clear. Variables such as the type of substance, the duration used, and the user’s health and age all impact the likelihood of developing a co-occurring physical or mental illness. Even in small doses, alcohol and drugs can impact the immune system, increasing the chances of a user becoming ill. Long-term use and abuse of drugs or alcohol can affect the brain and physiological systems of the body, giving bacteria, viruses, and cancers opportunities to create disease. The “invisible” diseases of the brain, like depression, anxiety, PTSD, and others also manifest and escalate when alcohol and drugs are used to self-medicate turbulent thoughts and moods.

For long-term recovery to take place, diseases and addictions must be treated simultaneously.

Dr. Mohammed Saeed, MD.

Dr. Saeed is a psychiatry specialist with over 40 years of experience in the medical field. He received training in General Psychiatry at the University of Texas Medical Branch, where he was selected as the Medical Director of the Division of Child and Adolescent Psychiatry. He currently serves as the medical director at Into Action Recovery Centers. Full Bio

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