Affective disorders, also known as mood disorders, are psychiatric personality disorders caused by emotional disturbances. Most affective disorders are endogenous, caused by changes in metabolic processes in the central nervous system.
Major depressive disorder is a mental disorder involving persistent low mood, low self-esteem, and loss of interest. It is not necessarily accompanied by bad mood, depression, or homesickness – masked depression. However, it is characterized by persistent disorders in social connections, changes in ideas of guilt and self-worth, and significant problems with weight, appetite, and sleep.
In contrast, bipolar disorder is alternating stages of mania and depression, accompanied by a sequential passage through stages of agitation, inhibition, and apathy. Bipolar disorder is a long-term illness for which the mania stage is mandatory.