It wasn't very long ago that most people considered addiction to be a moral failing rather than a treatable disease-it was largely thought that people who succumbed to drugs and alcohol were simply making poor decisions. Even when the American Medical Association announced in 1950 that alcoholism is a disease, people continued to hold onto the belief that addiction was voluntary. But now scientists have been able to pinpoint exactly what happens in the brain of an addict, proving that addiction is a disease and that the brain can make it very difficult for people to resist the effects of drugs and alcohol. As humans, we inherently enjoy feeling good. Under normal circumstances, neurons in the brain's reward pathway release a transmitter called dopamine, which controls movement, emotion, perception, motivation, and pleasure. Dopamine is then released into the synapse, which results in a jolt of pleasure. The sending cell takes back any excess dopamine, and other nerve cells release GABA, an inhibitory transmitter that prevents the receptor nerve from being over-stimulated. When drugs are used, the amount of dopamine in the synapse is increased, heightening the feeling of pleasure to the point of euphoria. Because the brain associates enjoyment with experiences that help us survive, the brain remembers what caused this feeling and wants to repeat it. So when drugs make us feel good, our brains want more. In addition, repeated drug use affects the functions of GABA, which keeps our nerves from being over-stimulated. With nothing to tell the brain it's had enough, the brain never thinks it's satiated, leading to repeated use and addiction. Certain drugs can increase dopamine levels up to ten times more than natural pleasure-causing behaviors, and the enjoyable effects can last longer, making the behavior more attractive to the brain. After using drugs like opiates, the brain produces less dopamine or reduces the number of dopamine receptors. This makes it harder for drug users to experience pleasure, and they need to take the drug to get that euphoric feeling back. Using all of this knowledge, scientists have begun to create drugs such as naltrexone that can reduce the cravings that drive an addict to relapse. Researchers are also looking into vigabatrin, a seizure disorder treatment that's marketed in 60 countries, though not yet the U.S., which boosts GABA. Two biotech companies in the U.S. are studying the drug's effect on methamphetamine and cocaine use, hoping that enhancing GABA in the brains of addicts could help them control their cravings. Stress is also a factor in addiction-animal studies have long shown that stress can increase the brain's desire for drugs. Even in non-addicts, stress puts people into "fight-or-flight" mode, making us more impulsive. Dr. Nora Volkow, director of the National Institute on Drug Abuse, told TIME magazine that "the part of the prefrontal cortex that is involved in deliberative cognition is shut down by stress...It's supposed to be, but it's even more inhibited in substance abusers." The good news, however, is that Volkow's studies found that, at least in some cases, the brain begins returning to its pre-drug state after a year of abstinence. In 1985, she began using scans to study the brains of addicts, tracking blood flow and dopamine levels, among other things. After the subjects had been clean for a year, she rescanned their brains and found that they had begun to return to their original states. In addition, researchers have found that it takes about 90 days-the length of many rehabilitation models, including AA-for the brain to "reset" itself. A Yale University study found that after an addict has abstained for at least 90 days, the brain gradually returns to its natural decision-making and analytical functions. "Addiction is a medical condition," says Volkow. "We have to recognize that medications can reverse the pathology of the disease." However, medications don't address the behavioral aspects of addiction, so medication alone is likely not the answer. Rehabilitation programs have high success rates, and researchers have found that programs like AA can be up to 40% effective when the treatment is ongoing. So while addiction really is all in our heads, the changes that occur in the brain can be reversed with treatment and rehabilitation.