Treating adolescents for major depression can also reduce their chances of abusing drugs later on, a secondary benefit found in a five-year study of nearly 200 youths at 11 sites across the United States.
Only 10 percent of 192 adolescents whose depression receded after 12 weeks of treatment later abused drugs, compared to 25 percent of those for whom treatment did not work, according to research led by John Curry, a professor of psychology and neuroscience at Duke University.
"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," Curry said.
The study found no such relationship when it came to thwarting alcohol abuse, however.
The researchers followed nearly half the 439 participants from the "Treatment for Adolescents with Depression Study" (TADS; 2000-2003), led by Dr. John March, chief of Child and Adolescent Psychiatry at Duke University Medical Center. TADS is considered the largest sample of adolescents who had been treated for major depression.
The participants analyzed by Curry's study were ages 17-23 at the end of the five-year follow-up study and had no preexisting problems with abusing alcohol or drugs.
"Onset of Alcohol or Substance Use Disorders Following Treatment for Adolescent Depression" (2004-2008), found that marijuana was the most prevalent drug used by study participants (76 percent); other drugs included cocaine, opiates and hallucinogens.
The adolescents must have had at least five symptoms for a length of time to be diagnosed with major depression prior to treatment: depressed mood; loss of interest; disruptions in appetite, sleep or energy; poor concentration; worthlessness; and suicidal thoughts or behavior.
The researchers said that improved mood regulation due to medicine or skills learned in cognitive-behavior therapy, along with support and education that came with all of the treatments, may have played key roles in keeping the youths off drugs.
The researchers were surprised to find no differences in alcohol abuse and do not have an answer for why. Curry thinks the prevalence of alcohol use among people ages 17-23 may be a key factor.
"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."
Alcohol abuse also led to repeat bouts with depression for some participants, he said.
"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. "And what we found out was that, for those who had both alcohol disorder and another depression, the alcohol disorder almost always came first."
Curry and co-author Susan Silva, associate professor and statistician in the Duke School of Nursing, believe more study is needed because the number of participants who developed drug or alcohol disorders was relatively small.
Also, there was no comparison group of non-depressed patients, so the researchers could not be sure that rates of subsequent drug and alcohol abuse disorders were higher than those for adolescents not treated for depression.
The study appears in the April-May edition of the Journal of Consulting and Clinical Psychology.
Explore further: Teen alcohol and illicit drug use and abuse examined in study