For patients with seasonal depression, or the “winter blues,” light therapy has become an effective way of easing some of their symptoms. Now, a new study is showing how light therapy goes far beyond that, and could also be used to treat major depressive disorder.

The study, published Wednesday in the journal JAMA Psychiatry, found that light therapy either alone or combined with antidepressants is an effective treatment for adults with major depressive disorder (MDD).

MDD is the second-ranked cause of disability worldwide, and is associated with a decreased quality of life and increased risk of mortality. It is estimated that MDD affects at least five per cent of the population, or one in 20 people.

Treatments for MDD include psychotherapy and antidepressants, but remission rates remain low, and doctors agree there is a need for more treatment options.

Light therapy is an evidence-based treatment for seasonal affective disorder (SAD), a type of depression that's related to changes in the seasons. Doctors commonly prescribe light boxes to patients with SAD. The devices start at about $100, and give off an artificial light that's similar to natural sunlight. Researchers believe this light causes a chemical change in the brain that helps ease symptoms of depression.

For the trial, 122 adults were recruited from psychiatric outpatient clinics in Toronto and Vancouver. The participants were all between the ages of 19 and 60, and all had been diagnosed with MDD.

The participants were randomized to four different treatment groups: light therapy and placebo antidepressants, placebo light therapy and antidepressants, a combination of light therapy and antidepressants, and a combination of placebo light therapy and placebo antidepressants.

Prozac was the antidepressant used in the trial, and participants were told to use a fluorescent light box for 30 minutes a day, at the start of their day. At the end of the trial, the participants were assessed for depression using a diagnostic questionnaire. These scores were then compared to baseline measurements.

The authors of the study found the following:

  • 55 per cent of patients using only light therapy or only Prozac saw their depression lift;
  • 76 per cent of patients using both light therapy and Prozac saw their depression lift.

Could light be used to treat different types of depression?

Dr. Raymond Lam, the study's lead author and a professor of psychiatry at the University of British Columbia, said that the trial was conducted during all seasons of the year, suggesting that light therapy could be used to treat different types of depression.

"It really does show that light can be used to treat different types of depression, not just 'winter depression'" he told CTV News.

Lam said more studies need to be done to confirm the trial's results. As well, future studies should examine how specifically light therapy should be prescribed to patients with depression.

Dr. Anthony Levitt, chief of the Brain Sciences Program at Toronto’s Sunnybrook Hospital, said light therapy is a fairly “innocuous” treatment for depression. However, he cautions that it may not be appropriate for patients with certain disorders, particularly bipolar disorder.

Meanwhile, Ken Porter, a program manager with the Mood Disorders Society of Canada, said he found the results of the study to be "encouraging."

"Any study that encourages treatment is worthwhile," he said. "We've seen individuals who've talked about the success of light therapy in the past, and having a study that confirms their feelings is quite beneficial."

With files from CTV's Medical Correspondent Avis Favaro and Senior Producer Elizabeth St. Philip