Three years ago, Marcia Sturm was walking her golden retriever, Bo, near her Los Angeles home. An employee from nearby Cedars-Sinai Medical Center approached her and asked if she would be interested in bringing Bo to the hospital’s AIDS unit to visit with patients. She was—and she and Bo have been a part of the POOCH (Pets Offer Ongoing Care and Healing) program ever since.

Bo is one of a growing number of “therapy dogs” visiting people in hospitals, nursing homes, mental health centers, and shelters, where they do everything from lift spirits to assist with physical therapy.

Evidence of positive responses to such animal-assisted therapy has mostly been anecdotal. But a recent study on elderly nursing home patients now offers scientific support that brief weekly visits from man’s best friend can have a positive therapeutic impact.