Addicted to Java

If the best part of waking up is coffee in your cup, chances are you're dependent on your morning brew -- and so is your family.

The jolt you get from drinking java or soda may seem small, but caffeinated drinks "can be addictive," says Kenneth Kendler, M.D. The news may be surprising to some, but likely makes sense to the many Americans who can't face the day without hitting Starbucks first.

"Caffeine likely performs like other psychoactive substances of abuse," he warns. And like its more hard-hitting counterparts, alcohol, cigarettes and drugs, its ill effects seem to depend partly on your genes.

Kendler, a professor of psychiatry at Virginia Commonwealth University Medical College, examined 1,000 sets of female twins to see if caffeine use ran in the family. He looked at several markers of caffeine addiction: whether the women used tea, soda or coffee heavily (did they drink 625 mg of caffeine, equivalent to five cups of coffee, a day?), how tolerant they were to it (did they find themselves needing to drink more than their usual amount to get a buzz?), and whether they experienced withdrawal (headaches, depression or nausea) when they stopped drinking the beverages.

Kendler found that the likelihood of inheriting a taste for caffeine is extremely high for women, as is their tolerance for it and the set of withdrawal symptoms they experience when they cease to drink it.

While coffee addicts have little to fear from their vice -- it causes few side effects -- Kendler points out that caffeine is not as benign as it seems. "Coffee is now seen as haute couture," he says, "but I see a touch of hypocrisy in people who drink four cups of coffee as they preach the evils of drugs or alcohol."