For as many as half of seniors with depression, drugs don’t work. But a new first-of-its-kind study finds a two-drug combo can help many of those with hard-to-treat depression.

The study, led by researchers at the Centre for Addiction and Mental Health in Toronto, tracked 468 people over age 60 diagnosed with depression. It found that adding a low dose of the antipsychotic drug aripiprazole (brand name Abilify) helped relieve symptoms of depression in patients for whom an antidepressant alone wasn't effective.

The research, published in The Lancet, also found the two-drug combination reduced the likelihood that they would have suicidal thoughts.

"This is a rare study because it looks at depression specifically in older adults," said Benoit Mulsant, M.D., a co-author of the study. "It's important to treat older adults effectively, especially given that adults with late-life depression are at an increased risk of developing dementia. Our research demonstrates that older adults respond to treatment for depression."

Depression strikes up to 16 percent of seniors, studies show. Elderly patients with clinical depression use more healthcare resources, are less able to live independently, and have a high risk of suicide. Depression is also a risk factor for dementia.

The new study was funded, in part, by the National Institutes of Health.