We sometimes throw around the word “addiction” a little loosely.  “I’m addicted to Harlequin Romances” someone might say, or, “I’m addicted to CBC Radio.”

True addiction, however, isn’t just doing something frequently because you enjoy it, or even a habit that’s hard to break:  it’s a complex condition that involves the brain’s biochemistry, genetic factors, social factors, and more.

Not everyone who smokes a cigarette, or drinks a glass of whiskey, or even shoots up heroin will become addicted to nicotine, or alcohol, or opiates.  But every addict began as a casual user, someone who discovered a substance that made him or her feel good.

Drugs produce a feeling of pleasure because by provoking temporary changes in the brain.  Specifically, they affect the “reward pathway”–linked areas of the brain central to feelings of pleasure. 

A central player in the reward pathway is a brain chemical called dopamine, released whenever we feel pleasure. Normally, dopamine is quickly reabsorbed.  Many addictive drugs, however, seem to block this process, causing dopamine levels–and the person whose brain they’re in–to remain high.

Chronic use of these substances over time can alter the brains of some people, leading to addiction.  One effect is tolerance: ever-larger doses are needed to achieve the same pleasurable effect.  Eventually, the brain becomes so altered that the feeling of pleasure can’t be generated at all; instead, the brain is so used to having the drug it can’t function without it, and so the addict actually requires the drug just to function.

That, in turn, leads to a fierce craving when the addict tries to quit. That’s one reason only 20 percent of addicts achieve a stable abstinence after a single detoxification attempt.  Craving can linger for months or years. 

Craving is also a conditioned response to people, places and activities associated with drug use, which is why recovering addicts are urged to avoid such things.  Negative mood states–depression, economic stress, the loss of a loved one–often contribute to relapses, too.  And when an addict relapses, he or she is likely to return to former or even heavier levels of drug use (alcoholics, for example, are likely to drink as if making up for lost time).

Stress seems to play a role in why some people become addicts in the first place; the more stress someone is under when he or she begins using drugs, the more likely he or she is to become addicted.  But genetics seems to play a role, too.

For instance, studies have found that people with a specific variant of a gene that regulates the brain’s levels of dopamine are much less likely smoke than people without that gene, and if they do smoke, probably started later, were less likely to start before age 16, and find it easier to quit.

People with that gene also displayed weaker novelty-seeking characteristics than those without it, and studies have shown that people who are drawn to novelty–are always looking for the next new thing–find it harder to quit smoking than those who aren’t.

We also know genes influence the attraction to caffeine–a third to two-thirds of a woman’s vulnerability to caffeine is apparently due to heredity, according a recent study.  (And yes, caffeine can be addictive:  if you need four or five cups a day to feel good, if you get a headache when you haven’t consumed caffeine for a while, if you need increasing amounts to get the same effect–then you’re using caffeine as a drug.  The biological processes aren’t really much different from what goes on in the brains of people addicted to alcohol or nicotine or heroin.)

And what about that other substance some people claim to be addicted to, chocolate?  Well, it certainly contains chemicals that affect the reward pathway of the brain.  But studies suggest the craving for is more cultural than physiological.  One recent study showed that while chocolate is the number-one craving among American women, far more so than among American men, in Spain, both sexes rated their desire for chocolate about the same, and the overall craving was lower than in the U.S.

In other words, we may crave chocolate more because of the marketing might of the chocolate companies than because we’re addicted to it physically.

Which reminds me–I sure could go for a Cadbury’s chocolate Easter egg right about now!

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