Psychological disorders are defined by the APA as significant disturbances in thoughts, feelings, and behaviors that lead to distress or disability. The DSM-5 classifies and diagnoses disorders based on symptoms. Perspectives include biological factors like genetics or brain abnormalities and psychosocial factors like learning or environment. The diathesis-stress model suggests some people are predisposed to disorders when faced with stressors. Common disorders are anxiety disorders, depression, PTSD, schizophrenia, and personality disorders.