Unipolar depression, otherwise known as major depressive disorder, is also a subtype of schizoaffective disorder. In this case, the term unipolar means that this version of depression does not cycle through mania or other mental states, but rather the individual tends to be at a low point continuously. This complex disorder has multiple causes: psychological, social, genetic, and interpersonal. Many do not entirely understand what causes depression, but it is understood that a chemical imbalance in the brain may be a strong factor. Certain neurotransmitters affect an individual's mood, such as norepinephrine, serotonin, and dopamine. Doctors and psychiatrists prescribe antidepressants to act on these chemicals in the brain and to improve depression. Schizoaffective unipolar type is characterized by symptoms of unipolar depression alongside psychotic symptoms and hallucinations.