The effects of drugs.

Cocaine, like methamphetamine, is a stimulant that can have powerful effects on the brain and body. But how does it affect the brain over a long period of time? Can you tell which of the PET images shown here is of a normal brain and which one is of a cocaine addict's brain? Neurons that are the most active metabolize more glucose and are shown in red. The image on the left is the brain of a person who had never taken cocaine. The image on the right shows how cocaine decreases the activity of the brain.

After taking cocaine, the high wears off after about 30 minutes, but the brain is not the same as it was before. Once a person is addicted to a drug like cocaine, the brain is affected for a long time. In fact, the brain really is changed. These PET images show how cocaine affects the brain even after a person stops abusing drugs. Look at the brain of a cocaine abuser ten days after the last use of cocaine. How does the brain compare to a normal brain, that is, the brain of someone who has not abused drugs? Like most of the PET images you have examined, these measure glucose utilization and tell us about brain activity levels. The areas in red are most active. Even ten days after the last abuse of cocaine, the levels of activity in a drug abuser's brain are much lower than those in the normal brain. How long do these changes in the brain last? Even 100 days after the last cocaine use, the drug abuser's brain is much less active than the normal brain. That is over three months later. Scientists wonder if there are areas in the brain that never fully recover from the effects of drugs.

Scientific investigations reinforce the fact that drug addiction is a brain disease. Drugs really do change the way the neurons in the brain work. Scientists don't know all of the answers, though. Researchers continue to investigate how drugs exert their effects. But they must deal with several issues that make answers more difficult to find. First, each person responds to drugs differently. Not everyone who experiments with drugs will become addicted. An individual's genetic makeup undoubtedly plays a part in determining whether a person becomes addicted to drugs. Second, many drug abusers abuse more than one drug. Individuals who take cocaine, for example, may also drink alcohol. Taking more than one drug at a time makes the consequences of drug abuse more unpredictable. Third, addicts often have other health problems in addition to drug addiction. Heroin addicts, for example, spend a lot of energy trying to get their next fix. Their search for drugs takes over their lives. They don't eat right. They may have weak immune systems, and they often suffer from mental illnesses such as depression.