|Issue 1 • Volume 1||
The Biology of Drug Addiction
By Bertha K. Madras, Ph.D.
This is the first in a series of articles on how drugs affect the brain and body. Specific drugs and their effects will be addressed in future articles.
The Magnitude of the Problem
Substance abuse places an enormous burden on society, causing or contributing to a host of medical, social, and criminal justice problems and can affect people at all stages of life. Prenatal exposure to drugs is linked to low birth weight and has been associated with developmental disorders. In adolescence and young adulthood, drug use can be associated with poor school performance, accidents, unplanned sexual activity and pregnancy, violence, and criminal activity. The work performance of illicit drug users is characterized by absenteeism, illness, injuries, low productivity, and job turnover. Older persons do not escape the long-term effects of drugs; addiction, compromised health, and interrupted educational and social development are issues in this population.
Drug use, abuse, addiction
A number of personal factors also can promote drug abuse problems. Examples include psychiatric conditions, personality disorders, poor school performance, inappropriate school behavior, and early drug use. There is also growing evidence that genetics may contribute approximately 50 percent of susceptibility to addiction, depending on the type of drug and the particular environment. It has been proposed that drug use and addiction are forms of self-medication, with users seeking to relieve depression, anxiety, grief, or severe psychiatric problems.
What is certain is that drug abuse can have different and more profound effects on a young person than an older person. According to Dr. Jean Lud Cadet of the Molecular Neuropsychiatry Branch at the National Institute on Drug Abuse and Dr. Mark S. Gold of the Department of Psychiatry, Neuroscience, Anesthesiology, and Community Health and Family Medicine at the University of Florida, the human brain takes at least 21 years to fully develop. Because the brain is still maturing during adolescence and young adulthood, and because drugs can change the programming responsible for the normal development of the brain, this population is particularly vulnerable to drug addiction.
The Cycle of Addiction
How do drugs affect the brain?
Drugs resemble, but are not identical to, the chemical messages produced by the brain. The “imposters” cocaine, amphetamine, and Ecstasy, for example, are similar to the brain chemicals dopamine, serotonin, and norepinephrine; THC (9-tetrahydrocannabinol), an active ingredient in the marijuana plant, resembles anandamide and 2-arachidonylglycerol, produced by the brain.
But because drugs do not precisely duplicate brain chemicals, the brain cannot control drug messages the same way it controls its own. The results, as the brain tries to process these “false” messages, are euphoria, delusions, hallucinations, anger, and a host of other strange sensations or behaviors.
With repeated frequent drug use, the brain can adapt to and compensate for abnormal signals, and it is not clear to what extent this adaptation is reversible. Drugs can change cell structure, metabolism, signaling, and networks. And some drugs, such as amphetamines, alcohol, and inhalants, are quite toxic to the brain. Long-term users of specific drugs may experience durable changes in brain function and behavior. Withdrawal from drugs can lead people to feel their brain is no longer normal unless they consume more drugs. During withdrawal, a variety of problems can emerge, including anxiety, irritability, misery, stress, and other psychological or physical discomfits, such as tremors or flu-like symptoms. Drug addiction can be viewed as a chronic, relapsing disease characterized by compulsive, uncontrollable use despite adverse consequences. At the same time, it is important to recognize the role of personal responsibility in determining whether the addictive behavior stops or continues. Drug-addicted patients, like patients with other diseases, are urged to assume responsibility for compliance with treatment.
Prevention, intervention, and treatment of addiction