The North American reference book used by psychiatrists and psychologists to diagnose and treat psychological disorders is known as the Diagnostic and Statistical Manual of Mental Disorders (DSM). It is produced by the American Psychiatric Association (APA). The most recent version was released in May of 2013 and is known as the DSM-5. The DSM is relied upon by clinicians, health insurance companies, medicine companies, and the legal system as a reference for understanding and identifying mental disorders. The DSM divides mental disorders into groups and provides descriptive signs and symptoms that define each disorder. In addition, it lists statistics for each disorder ranging from its frequency in the general population to the most effective form of treatment.