"What is exciting about these findings is that they are among the first to demonstrate that treating insomnia with a behavioral strategy, not a pill, can prevent the development of depression in older adults," said sleep specialist Wendy Troxel, a senior behavioral scientist at RAND Corporation, who was not involved in the study.

The study's findings are "highly significant" because major depression is very common among older adults and "is associated with an increased risk of cognitive decline, disability, suicide and all-cause mortality," Troxel added.

Numerous studies have shown that insomnia is a major risk factor for depression, and "some 30% to 50% of older adults complain of insomnia," said study author Dr.

Michael Irwin, a professor of psychiatry and biobehavioral sciences in the David Geffen School of Medicine at UCLA.

Adults in the randomized clinical trial who received cognitive behavior therapy for their insomnia were two times less likely to develop depression, Irwin said, adding that if remission from insomnia was sustained for three years, "there was an 83% reduction in the likelihood of developing depression."

"That's why this study is so important," Irwin said.

"We have shown that we can actually target insomnia with cognitive behavior therapy and prevent depression from occurring."

Therapist involvement was key

The study, published Wednesday in the journal JAMA Psychiatry, randomly split adults over age 60 with insomnia but without depression into two groups.