Army veteran Vivian Cooke has long struggled with debilitating depression. She has tried alternative therapies and medication to cope with her symptoms.

“It wasn’t effective. Some side effects would be headaches or stomachache,” she told CBS News.

Then three years ago, she decided to try something different after hearing about a study testing Botox to treat depression.

Get Breaking News Delivered to Your Inbox

While Botox is commonly used for cosmetic purposes, doctors say the reasoning behind the treatment for depression may not be what you expect.

“We don’t believe it has anything to do with looks,” says researcher Dr. Eric Finzi of Chevy Chase Cosmetic Center.

Rather, he says it’s because facial expressions are part of the circuit of the brain related to mood.

“Fear, anger and sadness — all go through this muscle,” Finzi told CBS News, pointing out the area between the eyebrows where frown lines appear. “So Botox basically inhibits the muscle and calms it down, so it becomes more difficult to feel those negative emotions.”

The makers of Botox recently announced plans for the final phase of testing it as a treatment for depression. Finzi notes previous studies show between 50 to 60 percent of patients may benefit from the treatment.

“Our hope is eventually it will form a place as one of the tools to treat depression,” he said.

Botox is a prescription drug that blocks nerve signals to muscles in the injection area. Its effects are temporary and typically wear off after three months. Botox is currently FDA approved for cosmetic use to lessen frown lines, and for medical use to treat a number of conditions including chronic migraines, bladder incontinence, excessive underarm perspiration, and certain types of neck pain and eye issues. Costs vary widely, but the American Society for Aesthetic Plastic Surgery said the average price for a Botox treatment in 2016 was $376.

Researchers are also studying whether Botox can treat social anxiety and bipolar disorder.

As for Cooke, she said she noticed a change in her depression almost immediately.

“I found overall my mood was better on a day-to-day basis,” she said. “I had less problems with depression.”

Even though the study she took part in is now over, she said she will continue to get Botox injections.