Final answer:
Major Depressive Disorder is characterized by persistent intense sadness, Bipolar I by manic episodes, and Bipolar II by hypomanic and depressive episodes, each with distinct implications for treatment and health outcomes.
Step-by-step explanation:
Major Depressive Disorder (MDD), Bipolar I, and Bipolar II are significant mood disorders, each with unique characteristics. Major Depressive Disorder is marked by persistent feelings of intense sadness and despair, changes in appetite, difficulty concentrating, and loss of enjoyment in activities, typically without the mood elevation seen in bipolar disorders. Bipolar I is distinguished by manic episodes that may lead to hospitalization or significant impairment, and depressive episodes are not necessary for the diagnosis but often occur. In contrast, Bipolar II involves a pattern of depressive episodes as well as hypomanic episodes, which are less severe than the full-blown mania of Bipolar I and do not involve psychosis. While treatments such as anti-depressants and psychotherapy can manage these disorders, they exhibit distinct presentations and implications for the individual's quality of life and health risks, such as heart disease.