Legal or illegal, drug abuse results in medical consequences: cancers, cirrhosis of the liver, heart disease and stroke, HIV, hepatitis and lung disease, to name a few. According to the National Center on Addiction and Substance Abuse at Columbia University, untreated addiction and risky use of drugs causes or contributes to more than 70 conditions requiring medical treatment. These effects of drug abuse are also responsible for 20 percent of all the deaths in the U.S.

Brain Effects

Addictive drugs flood the brain’s reward center with the neurotransmitter dopamine in amounts that are 2 to 10 times greater than those released during pleasurable activities, reports the National Institute on Drug Abuse, or NIDA. With continued use, brain chemistry changes and more of the drug is needed to produce the same euphoric experience. With some drugs, more is needed just to feel normal. When not taking the drug, users commonly experience depression that leads to compulsive drug use. Long-term substance abuse affects brain functioning, causing memory loss, learning difficulties and impaired judgment. Marijuana causes short-term memory problems. Alcohol shrinks the brain over time and increases the risk for dementia. Inhalants damage brain cells faster than any of the other substances.

Respiratory Effects

Inhaled substances, including tobacco, marijuana, crack cocaine, heroin and aerosols, damage the lungs. These substances cause coughing, chronic bronchitis, emphysema, and worsen asthma. In addition, heroin, narcotic pain killers and sedatives disrupt the drive to breathe and may cause respiratory arrest. Most deaths from obstructive pulmonary diseases and lung cancer are linked to smoking tobacco. Use of inhalants can cause asphyxiation as the concentration of inhaled fumes replaces the oxygen in the lungs.

Digestive Effects

Alcohol causes a wide range of damaging digestive system effects, including acid reflux, liver cirrhosis and inflammation of the stomach and pancreas. Sixty percent of cases of pancreatitis result from excessive alcohol intake, reports the Substance Abuse and Mental Health Services Administration. Liver damage is common with use of heroin, inhalants, anabolic steroids and alcohol. Cocaine abuse can lead to painful gastric ulcers and damaging reductions in blood flow to the intestines due to powerful blood vessel constriction. Nausea and vomiting often occurs shortly after drug use, and is a symptom of heroin and prescription drug withdrawal.

Cardiovascular Effects

Most abused substances have adverse effects on the cardiovascular system. Heroin and prescription drug use can slow or disrupt the heart rate to the point of death. Cocaine, methamphetamine, ecstasy and amphetamines can cause life-threatening effects, including an irregular heartbeat, increased blood pressure, stroke and cardiac arrest. Tobacco smokers are 2 to 4 times more likely to develop coronary heart disease than nonsmokers, warns NIDA. The risk for heart attack, stroke, circulatory problems and aneurysms is also increased for smokers.

Other Health Effects

Sharing injection equipment while using heroin, cocaine, steroids and methamphetamine puts users at risk for HIV, hepatitis B and hepatitis C. Risky sexual behaviors while under the influence also contribute to an increased rates of HIV, viral hepatitis and other sexually transmitted diseases. Other health issues due to injecting drugs are collapsed veins, infections of the heart and joints, and organ damage from reduced blood flow. Alcohol increases the risk for many cancers, including the mouth, throat, stomach, liver, lungs, pancreas and bladder. Tobacco use accounts for 90 percent of all lung cancers, notes NIDA.