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Big mystery: What causes addiction?

Why are some of us prone to addiction — be it alcohol, drugs or food — and others aren’t?
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Drunks beget drunkards, Plutarch noticed, summarizing what has been observed anecdotally for at least a couple of millennia. But why are some of us prone to addiction — be it alcohol, drugs or food — and others aren’t?

THOUGH THE exact mechanisms haven’t been identified, experts in alcoholism widely agree that some people are genetically vulnerable to developing the disorder. Sons of alcoholic fathers, for instance, are at three to four times the risk of abusing the drug. Generally, a predisposition to abuse one drug applies to almost all other drugs. Alcoholism, for instance, may be present in as many as three-fourths of cocaine addicts.

Still, no gene has ever been identified, and, even among men who carry a hereditary load, predisposing physical factors don’t doom them to a sodden or chemically dependent lifestyle. There’s no such thing as a pre-addictive personality, experts say.

So why do some people become addicted? Addictionologists have theorized that some people, particular those addicted to opiates, may have deficiencies in their brain reward systems — fewer natural opiates circulating, for instance, or fewer receptor sites. In addicts, the question eventually becomes moot, for years of abuse desensitizes their receptors, and they end up with altered pleasure thresholds.

Other drug users gravitate toward their “drug of choice” to “self-medicate.” Heroin, for instance, is remarkably effective at “normalizing” people who suffer from delusions and hallucinations (mostly schizophrenics). Cocaine can quickly lift a depression, or enable a person with attention-deficit disorder to become better organized and focused. For these people, addiction is a troubling side effect to their adaptive attempts to relieve their own suffering.


According to psychiatrists who have studied psychodynamic causes of drug addiction, the motivation to use psychoactive substances can often be traced to critical passages early in life. Says Edward J. Khantzian, a Harvard psychiatrist and author of the “self-medicating” hypothesis of drug addiction, many substance-dependent people who make it into therapy show a profound inability to calm and soothe themselves when stressed. The ability to self-regulate mood — to maintain psychic homeostasis — is a task learned between the ages of 1 and 3, when a toddler normally internalizes such a function from caring parents. Mothers, and no doubt many fathers, of frequent drug users have been described as “relatively cold, unresponsive and underprotective.” Regarding their children’s accomplishments, they send a very mixed message: They’re pressuring and overly interested in their children’s performance, yet rarely offer them encouragement.

Eating disorders, which are considered addictions and primarily affect women, offer a clear illustration of the self-regulation mechanism gone haywire. If the inability to soothe oneself is due to a distant or rejecting parent, compulsive eating is an attempt to make up for the loss, to construct a substitute attachment to a nurturing parent, with a primitive form of self-medication — food — one of the few things (in addition to love) that can calm a distressed child.

According to Robert B. Millman, a renowned addiction expert at New York Hospital-Cornell Medical School, locus of control is another influential factor in addiction vulnerability. “Addicts tend to believe that they are not the masters of their own fate, that control lies outside of them,” he says.

Narcissists are also well represented within drug-addicted populations: their self-absorption is so profound they don’t understand that the world outside them, which includes drugs, is real — and dangerous. Risk-takers are also vulnerable. “But there’s no way to tell which adrenaline junkie will get hooked on bungee jumping, venture capitalization or heroin,” says Millman.


While positive reinforcement — pleasure, getting high — entices a person to use a drug again after experimenting with it, continued use is often a function of so-called negative reinforcement. Tobacco smokers and opiate users experience this the most: Their motivation to use the drug is not to experience pleasure, but to relieve uncomfortable withdrawal symptoms.

Drug use is also often thought of as an escape — but becomes so in ways the abuser hadn’t planned on. Just as a compulsive gambler’s hyper-involvement in the betting process blocks out his personal problems, an addict’s pursuit of his drug becomes so monomaniacal that everything else, including the psychological pain that drove him to the drug, is forgotten.


Dr. George Koob of the Scripps Research Institute has a surprising new finding, cocaine does not just make users feel euphoric, but it simultaneously releases brain chemicals related to fear and stress — bad feelings that linger after the euphoria fades. “The only way to treat the bad feelings,” explains Koob, “Is to take the drug that makes you feel good again. But this becomes a vicious cycle.”

Even worse, changes in their brain make addicts crave drugs long after they have stopped using them. Dr. Anna Rose Childress, of the University of Pennsylvania, says the craving response can be triggered easily — even by watching films. “And the person is then again vulernable,” says Childres, “And that kind of vulernability is probably as long as the person’s memory.”

Researchers are still trying to figure out why some people undergo these brain changes and become addicted while others do not. The ultimate goal: to develop medicine to control the craving.

While there are still many unknowns, scientists believe they’re making progress.

“The biological knowledge is going to give us an edge that we simply couldn’t have had before now,” says Childress, “And that is very exciting.”

NBC’s Robert Bazell contributed to this report.