Drug addiction is a disease with behavioral and physiological symptoms. Drug addiction begins with compulsive drug use that progresses until patients feel they need their drug of choice to function. Over time, addicts require higher and higher doses of their drug to feed their addiction. Prolonged exposure to high doses of drugs, as well as the behavioral symptoms of addiction, cause profound effects on an addict's physical and mental health.
Brain Damage
One potential effect of prolonged drug use and addiction is brain damage. Some addictive drugs interact with specific proteins and cells within the brain and nervous system, leading to abnormal signaling of cells within the brain. Over time, this abnormal signaling damages the specific nerve cells of the brain, causing brain damage. Other drugs may significantly increase blood pressure, leading to an increased risk of a brain-damaging stroke. Several drugs -- including nicotine, cocaine, ecstasy and methamphetamine -- lead to brain damage over time, according to the University of Utah Genetic Science Learning Center.
Lung Damage
Drug addiction may also lead to lung damage. Drugs such as crack cocaine, marijuana, methamphetamine and heroin may be smoked, and excessive smoke inhalation damages lung cells, according to a 2001 study published in "Current Opinion in Pulmonary Medicine." Smoking draws toxic chemicals into the lungs, and prolonged exposure to these chemicals leads to lung irritation, damage and possible genetic mutations of cells in lung tissue. Over time, these accumulated mutations lead to abnormal cell growth and lung cancer development.
Depression
Another common effect of drug addiction is depression. Patients already suffering from depression have a higher risk of abusing drugs, which may lead to addiction, according to The Scripps Research Institute. Drug addiction also worsens depression. Drug addiction interferes with an addict's life, causing erratic behavior that may lead to job loss or financial instability -- further contributing to depression. This erratic behavior also negatively affects an addict's interpersonal relationships with coworkers, friends and family, leading to social isolation. This social isolation enhances the addict's depression. Patients suffering from depression related to their addiction may seek help in the form of individual or group therapy, as well as drug addiction rehabilitation.
