According to The World Health Organization, more than 300 million people worldwide struggle with depression. But a new study from BMJ Medical Journal finds exercise can be just as beneficial as other forms of therapy and drugs when it comes to mental health management. “I'm very big in mental health, aside from being a personal trainer. I believe that plays a big part in your physical health. They say stress is the hardest on the body and can kill you more than anything else,” said Jessica Rivers, a personal trainer.