SAN FRANCISCO (CBS SF) — Researchers are testing Botox as a new treatment for depression.

The makers of Botox just announced the final phase of testing for depression and social anxiety.

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Doctors say previous studies show between 50 to 60 percent of patients benefit from receiving the facial injections. They say facial expressions are part of the circuit of the brain related to mood.

“Fear anger and sadness all go through this muscle, so Botox basically inhibits the muscle and calms it down,” says Dr. Eric Finz, a Botox Researcher at the Chevy Chase Cosmetic Center. “So it becomes more difficult to feel those negative emotions.”

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Patients in the study reported an overall improvement in mood.

Botox got FDA approval 15 years ago for cosmetic uses. It is also used to treat migraines and excessive sweating.

Researchers are also testing to see if it can help patients with bipolar disorder.

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Botox is temporary and typically wears off after three months.