Abnormal psychology is the branch of psychology that studies people's emotional, cognitive, and/or behavioral problems. Although many behaviors could be considered as abnormal, this branch of psychology generally deals with behavior in a clinical context. Those in the field of abnormal psychology study unusual patterns of behavior, emotion and thought, which may or may not be understood as causing a mental disorder. Abnormal behavior may be demarcated as behavior that is disturbing, distressing, maladaptive and often cognitions. Statistical infrequency is an abnormality of a person's trait, thinking or conduct is classified as abnormal if it is rare or statistically unusual. Causes of abnormality usually associated with the disorders can be traced back to family, genetical and school related factors. Some biological causes may comprise Physical illness or disability.