Mental Problems or mental illness is a psychological or behavioral pattern generally associated with subjective distress or disability that occurs in an individual, and which is not a part of normal development or culture. A few mental disorders are diagnosed based on the harm to others, regardless of the subject's perception of distress. The causes are often explained in terms of a diathesis-stress model or biopsychosocial model. Mental disorders are conceptualized as disorders of brain circuits likely caused by developmental processes shaped by a complex interplay of genetics and experience.