A newly developed nasal spray has been found to treat depression.

New research from the Toronto-based Center for Addiction and Mental Health shows the spray delivers a protein peptide and holds promise as a potential alternative therapy.

The study, led by Fang Liu, M.D. and published online in the journal Neuropsychopharmacology, was found to have minimal side effects and is just as effective in relieving depressive symptoms as a conventional antidepressant.

Although earlier studies showed the peptide had to be injected into the brain to be effective, the Toronto researchers found it worked well, when delivered as a nasal spray.

"Clinically, we needed to find a non-invasive, convenient method to deliver this peptide treatment," said Dr. Liu.

The spray, developed by U.S. company Impel NeuroPharma, was shown to deliver the peptide to the right part of the brain to relieve depression-like symptoms.

"This study marks the first time a peptide treatment has been delivered through nasal passageways to treat depression," said Dr. Liu, a professor with the University of Toronto's Department of Psychiatry.

The peptide treatment affects two dopamine receptors in the brain, linked to major depression.

Depression, the most common form of mental illness, is one of the leading causes of disability globally. More than 50 percent of people living with depression do not respond to first-line medication treatment.

"This research brings us one step closer to clinical trials," said Dr. Liu. In ongoing lab research, her team is experimenting to determine if they can make the peptide break down more slowly, and travel more quickly in the brain, to improve its anti-depressant effects.