Numerous diseases can be caused by substance abuse. According to the National Institute on Drug Abuse, or NIDA---a division of the National Institutes of Health---although substance abuse is often voluntary at first, over time it can alter a person's gene expression and brain circuitry, affecting behavior and the ability to make voluntary decisions. NIDA states that prolonged substance abuse can significantly damage a person's health and affect many body systems.
Cancer
Lung cancer is a disease that can be caused by substance abuse. According to NIDA, drug abuse can lead to numerous respiratory problems, and cigarette smoking has been linked to bronchitis, emphysema and lung cancer. Marijuana smoke is also believed to cause serious respiratory problems, and the prolonged use of certain drugs---including inhalants, nicotine and prescription opiates---can slow down breathing, reduce the level of oxygen that can enter the lungs and make asthma symptoms worse. NIDA states that cigarette smoking is the most preventable cause of cancer in the United States and is associated with cancer of the mouth, neck, stomach and lungs. Chronic marijuana use also injures the lungs, exposing them to numerous carcinogens and promoting precancerous lung changes similar to tobacco smoke. According to NIDA, abuse of the following drugs may cause cancer: nicotine, marijuana and steroids.
Cirrhosis
Cirrhosis is a disease that can be caused by substance abuse. The Merck Manuals website states that prolonged liver damage can cause cirrhosis and that the most common cause of cirrhosis among Americans is alcoholism or the chronic abuse of alcohol. After heart conditions and cancer, cirrhosis is the most common cause of death among Americans between the ages of 45 and 65. According to the Merck Manuals website, cirrhosis is the "irreversible replacement of a large amount of normal liver tissue with nonfunctioning scar tissue," which impairs the liver's ability to regenerate or grow new liver cells. Common symptoms associated with cirrhosis include anorexia or a poor appetite, weight loss and malaise. An affected liver is unable to perform the following functions: break down metabolic waste products, generate bile salts to help digest fats, eliminate toxins and process drugs, among other functions.
Heart Disease
Heart disease can be caused by substance abuse. According to the Women's Heart Foundation, the results of many studies suggest that moderate alcohol consumption may protect a person from heart disease by boosting HDL cholesterol and decreasing plaque buildup in the arteries. Consuming more than three drinks per day, however, has a toxic effect on the heart, and prolonged, heavy drinking can damage the heart and cause hypertension, or elevated blood pressure, alcoholic cardiomyopathy, or an enlarged and weakened heart, congestive heart failure and stroke. According to the American Heart Association, moderate alcohol consumption means an average of one to two drinks per day for men and one drink per day for women. One drink can be 12 oz. of beer, 4 oz. of wine, 1.5 oz. of 80-proof spirits or 1 oz. of 100-proof spirits.
