unipolar vs bipolar

Compare and contrast the symptoms of unipolar depression and bipolar disorder, including a clear distinction between sadness, depression, and mania. While there are a variety of psychological views offered to explain the development of depression (psychodynamic, behavioral, cognitive, and sociocultural), which do feel is the most compelling explanation and why? Given the strong evidence for the biological model of depression (as well as mania), why do you think some clients refuse biological interventions?