Looking to understand the scientific basis for what happens to the body during a depressive episode led researchers to experiment with adult stem cells from people suffering from major depressive disorder. What they learned is how omega-3 fish oil created an antidepressant response in the cells and helps all people regardless of whether they are prone to respond to pharmaceutical drugs.

These findings shed more light on previous studies showing the efficacy of omega-3s in the treatment of depression. Other trials, including double-blind, placebo-controlled trials, considered the gold standard in studies, have found omega-3 fish oil is effective in helping people who suffer from depression.

The study was published in the journal Molecular Psychiatry and was conducted by a team of researchers from the University of Illinois-Chicago interested in understanding how patients respond to medication.

According to the principal researcher Mark Rasenick, the study revealed some novel findings that will help scientists better comprehend the inner workings of the brain and why some people safely respond to antidepressants while others experience limited or no benefits from drugs designed to control depression. "It was also exciting to find scientific evidence that fish oil—an easy-to-get, natural product—may be an effective treatment for depression," he said.

Depression, or major depressive disorder, is the most common psychiatric disorder diagnosed. It is estimated about one in six people will experience at least one major depressive episode during their life. Doctors generally treat it with antidepressants but they are ineffective in approximately one of every three patients.

Scientists took skin cells from adults with depression. Those skin cells were converted to stem cells and then used to develop nerve cells. There were two sets of patients who donated skin cells – those who previously responded to depression treatment and those for whom the treatments did not work. In both cases the omega-3 fish oil provided an anti-depressant response.

While the response in the lab was similar to what was seen from prescription medication, Rasenick noticed it was produced through a different mechanism when omega-3s were used.

"We saw that fish oil was acting, in part, on glial cells, not neurons," Rasenick said. "For many years, scientists have paid scant attention to glia—a type of brain cell that surrounds neurons—but there is increasing evidence that glia may play a role in depression. Our study also showed that a stem cell model can be used to study response to treatment and that fish oil as a treatment, or companion to treatment, for depression warrants further investigation."

Click here to read more in the journal Molecular Psychiatry.