The illness tends to occur in women more often than in men and affects women later in life than in men. Men with the disorder tend to have antisocial personality traits. When the illness occurs earlier in life, it tends to have the bipolar component, whereas later in life it tends to have the depressive component. Generally, the disease begins in early adulthood. Additional symptoms may include the person being unable to follow a moving object with his or her eyes, and an early onset of rapid eye movement during sleep. The exact cause of the illness is unknown. It may involve a chemical imbalance in the brain or could be the result of factors affecting in utero development.

Treatment options vary depending on whether or not the patient is in a psychotic state. If this is the case, antipsychotic medications are used as antidepressants take a few weeks to start working. However, antidepressants are used to treat the mood disorder part of the disorder after the psychosis has ended. In some cases, electroconvulsive therapy (ECT) may be used. Overall, antipsychotic medications may be the most effective treatment for this disorder, although ongoing research is continuing on treatments. Psychoanalysis is also used. In patient care may be required if the person is a threat to him or herself or to someone else.

The prognosis for those with schizoaffective disorder is somewhere between the two types of illnesses. It is better than for those with schizophrenia, but worse than for those with a mood disorder alone.