A method of treating a mental disorder including administering to a patient in need thereof, an effective amount of a pharmaceutical composition including 1,1-diphenyl-4-piperidine-1-ylbuthan-1-ol or a pharmaceutically acceptable salt thereof. The mental disorder is depression, bipolar disorder, anxiety disorder, impulsive disorder, bulimia, panic disorder, social anxiety disorder, insomnia, attention deficit hyperactivity disorder (ADHD), schizophrenia, dementia, personality disorder, alcoholism, dissociative disorder, sleep apnea syndrome, or fibromyalgia. In a preferred embodiment, the mental disorder as a therapeutic target is fibromyalgia, chronic fatigue syndrome (CFS), or depression with pain, and the administration of the pharmaceutical composition is capable of reducing the pain caused by these diseases.
