Yoga therapy has been used to treat a broad range of mental conditions such as anxiety and depression for a long time. In Dr. Tim McCalls book, Yoga as Medicine, he devotes several chapters to this topic and provides many studies and references.
Yoga is a useful method to calm the mind and relax the body. The isometric aspects of holding, stretching and releasing muscles is very similar to the familiar progressive relaxation training techniques commonly used in Behavioral therapy.
The meditation aspects of yoga are quite similar to aspects of hypnosis. Sitting quietly and repeating a word or phrase has a quieting and calming effect on the mind and body.
The breathing aspects of yoga is the same as breathing used in cognitive-behavioral therapy to help clients reduce stress or as part of the tools used in reducing fears and phobias.
The philosophy of yoga with its emphasis on staying present and being aware of things without judging them is often incorporated into major mental health approaches such as dialectical behavior therapy, acceptance and commitment therapy, Rational Emotive Therapy and Cognitive-behavioral therapy.
Yoga therapy has broad appeal to clients and therapists alike. Beyond talk therapy, active and experiential approaches that combine talking with doing are well tolerated and often helpful in improving mood states.
I practice yoga personally and while I have used the breathing components of yoga for years with clients, have more recently introduced them to the attitudes and principles associated with the practice and found it to be a useful addition to my toolbox of mental health tools.
As yoga continues to grow in popularity and acceptance, no doubt, yoga therapy for the treatment of anxiety, depression and other mental health problems will also become a more popular form of treatment or used in conjunction with other systems of therapy and counseling.