Diagnosis according to the DSM-5 - The individual must experience at least 6 months of significant impairment in occupational, interpersonal, and self-supportive functioning. The individual must have experienced a period of actively psychotic symptoms without the presence of a depressive or bipolar disorder, Autism Spectrum Disorder, a communication disorder, or medical condition. Two or more of the following must be present in order to diagnosis Schizophrenia: 1) delusions, 2) hallucinations, 3) disorganized speech, 4) severely disorganized or catatonic behavior, and 4) negative symptoms. At least one of the symptoms has to be (1), (2), or (3).

Neuroleptic medications are used to treat the symptoms of Schizophrenia. The newer antipsychotic drugs tend to have fewer side-effects and better efficacy. However, medication tends to treat only the positive symptoms and appears to have little impact on negative symptoms. (Just to clarify, positive symptoms are just that, symptoms that are active - delusions, hallucinations and bizarre behavior. Negative symptoms are characterized by a "lack" of behavior - withdrawal, flat affect, and thought-blocking.)

Let's look at a case and determine whether or not this client might meet the criteria for Schizophrenia.

Billy Jean has been acting strangely for a couple of months now. She reports that her neighbors are trying to poison her. They are trying to give her poisoned food and have attempted to pump poisoned gas into her apartment through the air conditioning vents. She states that her mother is in collusion with the "group" that is after her - as are the neighbors. Billy Jean appears very nervous and has pressured speech. She appears confused and frightened.

The likely diagnosis is Delusional Disorder, not Schizophrenia, for the following reasons: First, the duration is too short for Schizophrenia (but is sufficient for Brief Psychotic Disorder or Schizophreniform Disorder). Next, while there may be an absence of hallucinations in Schizophrenia, this is relatively rare. Auditory hallucinations in the form of voices are most common, visual are the next common, and olfactory and kinesthetic are rare. Olfactory hallucinations are suggestive of organicity. A patient might have a residual or prodromal presentation that could look similar to the above case. However, the residual phase must (by definition) be preceded by an acute phase. In this case, the course and duration do not fit. The prodromal phase (meaning the period between the first appearance of symptoms and the acute state) is usually characterized by odd behavior and thinking, not clearly defined delusions.