Psychosis is the most serious and incapacitating degree of mental illness. Emotional problems with symptoms of anxiety or depression, or both together, are called _affective disorders_. People who have affective disorders make up the majority of clients seen by most psychotherapists; these clients are _not_ out of touch with reality. The problems that they have--though painful and sometimes obstacles to normal living--are essentially different from the difficulties that patients with psychoses have. Though there is no unanimity about this among health care professionals, we will distinguish between these two kinds of problems by calling a psychosis a _mental illness_, as opposed to an _emotional disorder_. It is a matter not only of degree but of kind. A person who is severely depressed or extremely anxious is usually still able to communicate rationally, and distinguish what is real from what is fantasy or delusion. Psychoses, on the other hand, are disorders that impair a person's abilities to think, remember, communicate, respond with appropriate emotions, interpret reality coherently, and behave in a reasonably "normal" way. People with psychoses {235} often have difficulty controlling their impulses, and their moods may change quickly and radically. Psychotic individuals often believe things to be true that are not, and they may hear sounds or voices that are not there. There are many theories about the causes of psychosis. Recently, research studies in psychiatry have shown that psychosis may be due to an excess of certain chemical substances called _neurotransmitters_ (such as norepinephrine or dopamine) in the brain. Another theory is that the brain of a psychotic person may be excessively sensitive to the action of certain neurotransmitters. The antipsychotic drugs, or neuroleptics, reduce the brain's sensitivity to one or more of these chemical substances. Some of the best-known antipsychotic drugs are these (trade names): Compazine Haldol Mellaril Prolixin Stelazine Thorazine Trilafon Vesprin Antipsychotic drugs frequently can clear thought processes, reduce or end hallucinations, relieve agitation and anxiety, and generally help patients return to the world of reality, communicate with others, and behave in a more reasonable and stable way. Antipsychotic drugs have many possible side effects. They may produce drowsiness, dizziness and nausea, fainting, muscle tremors, a shuffling gait, blurred vision, insomnia, sensitivity of the skin to sunlight, and other effects. Particularly disturbing side effects can often be avoided by changing to a different medication. Some people with psychotic symptoms may need to take antipsychotic medication for only a few weeks or months. Recurrent or chronic illnesses, however, may require drug treatment over a long period. WHEN DRUG THERAPY IS APPROPRIATE