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 (disability), and which is not a developmental or social norm. 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 the rest of the nervous system, often in a social context. Mental disorder is one aspect of mental health. The scientific study of mental disorders is called psychopathology. The causes of mental disorders are varied and in some cases unclear, and theories may incorporate findings from a range of fields. Services are based in psychiatric hospitals or in the community, and assessments are carried out by psychiatrists, clinical psychologists and clinical social workers, using various methods but often relying on observation and questioning. Clinical treatments are provided by various mental health professionals. Psychotherapy and psychiatric medication are two major treatment options, as are social interventions, peer support and self-help. In a minority of cases there might be involuntary detention or involuntary treatment, where legislation allows. Stigma and discrimination can add to the suffering and disability associated with mental disorders (or with being diagnosed or judged as having a mental disorder), leading to various social movements attempting to increase understanding and challenge social exclusion. Prevention is now appearing in some mental health strategies.