Your bodies chemistry and nutrition can actually cause disorders in mental conditions. Lack of sleep can also make you behave abstractly. Make sure your diet and nutrition are up to par as well as your exercise. Serotonin levels increase when you pay attention to these aspects of your life. Serotonin increases your feelings of happiness which helps your disorder.
St. John's Wart has been proven to help medium grade depression. For any other mental illness, it is best to seek professional medical advice and prescription medication. Do not self treat mental disorders.