Mental disorders are also known as psychiatric disorders. There are different types that induce, depending on the disease, discomfort in daily life and more or less severe suffering or behavioral disorders. The WHO defines these disorders as “psychiatric illness” or diseases that appear primarily as abnormalities of thought, feelings, or behavior, causing distress or dysfunction. Their manifestations most often appear in adolescence and early adulthood. Among these diverse pathological situations are depression, schizophrenia, bipolar disorder, borderline personality disorder, attention-deficit hyperactivity disorder, and autism spectrum disorder. The majority of clinical studies use a classification system regularly updated, recorded in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV 1994 revised in 2000), internationally accepted and published by the American Psychiatry Association. In Europe, a close system, the International Classification of Diseases, established by WHO, is also used.