Alcohol
Credit: Getty Images

Alcohol isn't as addictive as illegal drugs like heroin or crystal meth, but it's still highly dangerous. "Even though the drug itself isn't tremendously addictive, alcohol poses an enormous problem because so many people use it in a harmful way," says Dr. Andrew Kolodny, an addiction expert and chief medical officer of Phoenix House Foundation in New York City. "Many men engage in risky drinking, or binge drinking, which means more than four drinks at one sitting or more than 14 drinks a week."

Regular binge drinking can easily give way to addiction. "Some people are addicted to alcohol right away, but for most people, it takes a while for the addiction to develop before they start going downhill," says Jane Maxwell, of the Addiction Research Institute at University of Texas at Austin.

If alcoholism runs in your family, you're automatically at greater risk. "Alcohol addiction is unique in that there's a strong genetic component," Kolodny says. Experts don't know why heredity matters so much more with alcoholism than with addictions to other drugs, but there's a definite link.