Lindsay Lohan: Addiction

The fast-paced, partycentric world of young celebrity has vaulted many rising film stars into struggles with substance abuse and addiction. Drew Barrymore may have been the youngest teen star to succumb to drug and alcohol problems. She entered rehab at age 13, an experience she described in her 1991 memoir "Little Girl Lost." The treatment helped Barrymore, now 32, regain her balance, and she now has a thriving film career in blockbusters like "Charlie's Angels."

Another talented former child actress hasn't yet been as fortunate. Lindsay Lohan, the 21-year-old star of last summer's "Georgia Rule" (which co-starred Jane Fonda), has spent much of the last year in and out of rehab facilities. In a statement released after Lohan was caught driving drunk without a license in August, the troubled beauty said, "It is clear to me that my life has become completely unmanageable because I am addicted to alcohol and drugs." She recently checked out of a facility in Utah.

What causes addiction in teens and young adults? At the start, using drugs or alcohol is a voluntary thing—perhaps one buttressed by peer pressures—but a choice nonetheless. But Lucinda Miner of the National Institute on Drug Abuse explains that for those who become addicted, the ability to say no erodes as the substance they're using changes how their brains function. It may have something to do with drugs and alcohol damaging the prefrontal cortex, the brain's hub for decision making, but research hasn't yet pinpointed the connection.

About half the variation in addiction—the difference between those who drink alcohol but do not develop a dependency and those who do—is due to genetics, meaning that things like drug dependency and alcoholism often run in families. (Both Lohan and Barrymore have fathers who have struggled with alcoholism.) Environment also plays a significant role; Miner says that teens who move in circles where substance abuse is acceptable are much more likely to become addicted themselves.

While there are no national statistics on how many teens struggle with addiction, the latest data from the National Survey on Drug Use and Health estimates that 6.1 percent of teens between 12 and 17 need treatment for alcohol use; 5.4 percent of the same age group need treatment for illicit drug use.

And for adolescents and young adults who imbibe too much too young, the consequences can be lifelong. "Early exposure to substances can do very different things and poses different risks," says Miner. Since the brain is growing and wiring itself through the early 20s, damage done in the teenage years can seriously impede that development. Substance use at a younger age is a high risk factor for developing drug and alcohol dependencies later in life; people who drink before the age of 15, for example, are about four times more likely to become alcoholics.