in addition, there may be feelings of worthlessness, guilt, reproach, and loss of hope. a less severe but more long-term type of depression has been labeled dysthymia. while not as disabling as major depression, there is a chronic lowering of feelings of happiness, productivity, and energy. bipolar disorder is a less prevalent from of depression that involves cycling from periods of depression to periods of mania, which may include inappropriate elation, irritability, or social behavior; increased agitation and activity in thoughts and actions; insomnia; and grandiose thinking or poor judgment. the heterogeneity of depressive disorders may best be understood as the result of the interactions between biological, psychological, and social factors.