A mental disorder, also called a mental illness or psychiatric disorder is a mental or behavioral pattern or anomaly that causes either suffering or an impaired ability to function in ordinary life, and which is not developmentally or socially normative. Mental disorders are generally defined by a combination of how a person feels, acts, thinks or perceives. This may be associated with particular regions or functions of the brain or rest of the nervous system, often in a social context. Mental disorder is one aspect of mental health.

Anxiety or fear that interferes with normal functioning may be classified as an anxiety disorder.  Other affective (emotion/mood) processes can also become disordered.  Patterns of belief, language use and perception of reality can become disordered (e.g., delusions, thought disorder, hallucinations). Personality—the fundamental characteristics of a person that influence thoughts and behaviors across situations and time—may be considered disordered if judged to be abnormally rigid and maladaptive. Although treated separately by some, the commonly used categorical schemes include them as mental disorders, albeit on a separate "axis II" in the case of the DSM-IV. A number of different personality disorders are listed, including those sometimes classed as "eccentric", such as paranoid, schizoid and schizotypal personality disorders; types that have described as "dramatic" or "emotional", such as antisocial, borderline, histrionic or narcissistic personality disorders; and those sometimes classed as fear-related, such as anxious-avoidant, dependent, or obsessive-compulsive personality disorders. The personality disorders in general are defined as emerging in childhood, or at least by adolescence or early adulthood. Eating disorders involve disproportionate concern in matters of food and weight. Categories of disorder in this area include anorexia nervosa, bulimia nervosa, exercise bulimia or binge eating disorder. Sleep disorders such as insomnia involve disruption to normal sleep patterns, or a feeling of tiredness despite sleep appearing normal. Sexual and gender identity disorders may be diagnosed, including dyspareunia, gender identity disorder and ego-dystonic homosexuality. Various kinds of paraphilia are considered mental disorders (sexual arousal to objects, situations, or individuals that are considered abnormal or harmful to the person or others). People who are abnormally unable to resist certain urges or impulses that could be harmful to themselves or others, may be classed as having an impulse control disorder, and disorders such as kleptomania(stealing) or pyromania (fire-setting). Various behavioral addictions, such as gambling addiction, may be classed as a disorder. Obsessive-compulsive disorder can sometimes involve an inability to resist certain acts but is classed separately as being primarily an anxiety disorder. The use of drugs (legal or illegal, including alcohol), when it persists despite significant problems related to its use, may be defined as a mental disorder. People who suffer severe disturbances of their self-identity, memory and general awareness of themselves and their surroundings may be classed as having a dissociative identity disorder, such as depersonalization disorder or Dissociative Identity Disorder itself.

Rolando Larice & Associates offers treatment for mental health disorders in St. Louis with a wide array of services including primary care for physical wellbeing, psychiatric care for medication and psychological wellbeing, and counseling for mental wellbeing. Our multi-disciplinary team allows patients access to a comprehensive set of solutions for their treatment of mental health disorders and ongoing care. Mental health disorders do not have to be debilitating and can often be treated by appropriate healthcare professionals