ALBANY, N.Y. (The New York Times News Service) -- The science of addiction is as stark as multicolored scans of the brains of chronic alcoholics.

An addict's brain looks different. It has atrophied and shrunk.

The prefrontal cortex, with its decision-making function, lights up like a bonfire with rapid-firing synapses linked to craving and compulsive behavior.

In color MRI images, an average person's brain resembles a broad meadow of soft green, with pockets of soothing yellow and a few flecks of red.

An addict's brain is marked by large, fiery explosions of red embedded in a sea of harsh yellow surrounded by small islands of green. It is a brain under siege.

Scientists can measure the effects of this brain disease.

Addiction is not a character flaw or sign of moral weakness, they note, and it's not exclusive to humans. In experiments with lab mice, the rodents will continue to take ever-increasing amounts of alcohol and drugs until they die.

"A compulsive behavior in the face of negative consequences" is a definition of addiction preferred by Rochelle Schwartz-Bloom, professor of pharmacology at Duke University Medical Center.

"Addiction is a chronic, relapsing disorder. The brain structure and how it works is changed by long-term alcohol and drug abuse," said David Friedman, co-founder and director of the Addiction Studies Program at Wake Forest University of Medicine. He addressed a group of journalists in June in Reno, Nev., at the annual meeting of the College on Problems of Drug Dependence, a group of 700 leading researchers in the field of addiction.

Friedman and his colleagues described what amounted to a case study of Poppy's troubled life and erratic behavior.

Certain factors determine who becomes addicted: There is a strong genetic connection, with 50-100 genes being studied that may play a key role. Environmental factors are critical, including how much time a person spends with other alcoholics and accessibility to alcohol and drugs. The seeds of adult addiction are planted in an adolescent's still-developing, uniquely vulnerable brain.

"Drug abuse is voluntary behavior, but drug addiction is not," Friedman said, noting that about 10 percent of the people who occasionally abuse alcohol or drugs will become addicted.

Drug addicts pass through a period of abuse, but it's not easy to become addicted, Friedman noted. As a person becomes an addict, he starts to crave alcohol and drugs overwhelmingly. Behavior grows increasingly compulsive as the addict ends up physically and psychologically dependent.

Day in and day out, in a variety of ways, an addict's brain is telling him that he can't live without drugs or alcohol, setting off a spiral from which it is difficult to recover.

Addiction treatment is a complex and challenging proposition, with a high rate of failure and relapse. Successful treatments are as individual as the addict.

"One size does not fit all," said Douglas Marlowe, senior scientist at the Treatment Research Institute in Philadelphia.

"Changing a compulsive behavior like addiction involves changing short-term and long-term actions."

There are no shortcuts to sobriety, no magic pills or cures. A combination of medication and treatment has shown effectiveness in recent years. Naltrexone, a drug originally marketed for the treatment of heroin addiction, blocks alcohol craving and reduces alcohol consumption. Side effects are mild and quickly pass. Many alcoholics frequently fail to take their daily pill of naltrexone, which costs about $120 a month. A once-a-month injectable form, depot naltrexone, has proven effective, but it costs roughly $700 a month.

"The people who need depot naltrexone most are too poor to afford it," said Dr. Thomas Kosten, a medical doctor and chairman of psychiatry and neuroscience at Baylor College of Medicine. But a typical chronic alcoholic has three hospitalizations each year, and insurance companies are beginning to pay for depot naltrexone because it can reduce hospitalizations and save money -- yet only for people with health insurance.

"There is no simple solution to addiction," said Deni Carise, a director of the Treatment Research Institute in Philadelphia.

"It is a lifelong chronic illness that requires a complete lifestyle change, just like obesity and diabetes."

Copyright 2009 The New York Times News Service. All rights reserved.