A licensed mental health professional administers a test to determine severe depression. Symptoms are measured based on the Diagnostic and Statistical Manual of Mental Disorders, which helps practitioners diagnose and treat depression. Insurance companies establish reimbursement policies according to the same criteria, the Mayo Clinic states.
To meet the severe depression criteria, a person must exhibit five of seven symptoms over a period of time, usually two weeks, on a daily basis. Feeling sad, losing interest in regular activities, and suicidal thoughts or attempts are cardinal indicators of depression. Other criteria include disturbed sleep patterns, changes in weight or appetite, a sense of worthlessness or guilt, decreased energy levels, and disrupted concentration, according to the Mayo Clinic.