A psychologist is a medical doctor who trained in diagnosis, and treatment of a mental illness including schizophrenia, behavioral problems, learning difficulties, depression, and anxiety. Psychologists provide a wide range of treatments including psychological treatment also called psychotherapy or talking therapy, medication, behavioral, cognitive, cognitive-behavioral, interpersonal, humanistic, and psychodynamic therapy. A psychologist may also use the Diagnostic and Statistical Manual (DSM) criteria to diagnose the mental disease.