Treating depression in adolescents could lead to prevention of drug abuse in later life, says a new study.

The study found that only about 10 percent of nearly 200 participants who bounced back from depression used illicit drugs later in life compared to 25 percent of youngsters who were depressed even after treatment.

"It turned out that whatever they responded to -- cognitive behavioral therapy, Prozac, both treatments, or a placebo -- if they did respond within 12 weeks they were less likely to develop a drug-use disorder," said John Curry, a professor of psychology and neuroscience at Duke University.

Depression that remains even after treatment in called treatment-resistant major depressive disorder or MDD. Previous studies have found that adolescents with this type of depression are more likely to be drug abusers.

"It does point out that alcohol use disorders are very prevalent during that particular age period and there's a need for a lot of prevention and education for college students to avoid getting into heavy drinking and then the beginnings of an alcohol disorder," Curry said. "I think that is definitely a take-home message."

Treatment for MDD should include assessment of alcohol or drug abuse before the treatment and must be continuously monitored, the study says.

The study was conducted over a period of five years. The researchers say that half of the study group experienced a relapse of depression.

"When the teenagers got over the depression, about half of them stayed well for the whole five-year period, but almost half of them had a second episode of depression," Curry said.

Treatments might improve chances of reducing substance use among depressed teens but not alcohol use.

"And what we found out was that, for those who had both alcohol disorder and another depression, the alcohol disorder almost always came first," he added.

The study appears in the Journal of Consulting and Clinical Psychology.