Both cognitive-behavioral therapy and problem-solving therapy are intended to change negative thinking in order to alter mood and behavior.
After completing each exercise, participants in the intervention group received written individualized feedback from an online trainer. The trainers did not offer any therapeutic advice, only motivation and encouragement to continue the exercises. Participants also could repeat the online sessions as often as they liked.
The control group received information about depression but was under no obligation to read it.
The study, which was conducted by researchers from Leuphana University in Lueneburg, Germany, recruited 406 people with subthreshold depression, which is defined as having some symptoms of depression but not enough to be diagnosed with major depressive disorder. It was published Tuesday in JAMA, the journal of the American Medical Association.
Of the 406 participants that began the study, 335 completed the telephone follow-up at the end of 12 months. Twenty-seven percent in the intervention group experienced depression compared with 41 percent in the control group.
It is unclear if the people who went on to develop major depressive disorder had experienced it before. Lead author Claudia Buntrock, a PhD candidate in clinical psychology at Leuphana, says that because the study only tracked participants' mental health over the course of 12 months, the long-term effectiveness of the intervention is unknown.
It's also not clear if this kind of program could be scaled up. It took the trainers about 30 minutes to provide feedback for each session, and they also stayed in touch with participants via instant messaging, Buntrock says.
Other experiments with online therapy have found that people didn't continue it if it wasn't guided by an actual human. One reason could be that when people are depressed, they can have a hard time getting motivated to do things.
"More studies are needed to evaluate the preventive effects of unguided web-based interventions on the onset of major depressive disorder," Buntrock wrote in an email. Still, Buntrock seems pleased with the results, especially since the German insurance company BARMER GEK that sponsored the trial is now providing it to its customers.
"I was surprised by the big response to our study," Buntrock wrote. "And of course, I'm surprised about what happens now; that a health insurance company offers the intervention to its members. It's a success story you might dream of when you start, but it actually seeing to happen is a great feeling."
Copyright 2016 NPR. To see more, visit http://www.npr.org/.