It is crucial to realize that schizophrenia is not the cause of all psychotic symptoms. Psychosis is a general term used to describe psychotic symptoms whereas schizophrenia is a type of psychosis. In addition to schizophrenia, psychotic symptoms may result from a variety of causes, including brain trauma, strokes, tumors,  infections,  or the use of illegal drugs.  Misdiagnosis is common in schizophrenia for precisely this reason. Mental health professionals may require several months (or years) in order to determine that the cause of psychotic symptoms is schizophrenia and not some other condition.

Indeed, assessing a patient with psychotic symptoms can be a challenging task. Clinicians and researchers typically go through a process of “ruling out” other disorders before confirming a diagnosis. In addition to brain trauma, there are other mental disorders in which symptoms appear very similar to those of schizophrenia. Sometimes there are more appropriate diagnoses for individuals with psychotic symptoms.

For example, some patients with psychotic symptoms also have depression. When this is the case, a clinician must consider a diagnosis of schizoaffective disorder. Alternatively, the use of some illegal drugs may mimic psychotic symptoms.  In order to determine that the symptoms are truly those of schizophrenia, it is important to determine that the patient has not been using substances that can cause these behaviors. Some other disorders in which psychotic symptoms are prominent follow.

Schizoaffective Disorder. Schizoaffective disorder is characterized by both schizophrenia and severe mood disorder symptoms. Someone with schizoaffective disorder meets diagnostic criteria for schizophrenia and at the same time experiences severe moods and marked changes of mood.

Schizophreniform Disorder. In order to receive a diagnosis of schizophrenia, one must exhibit psychotic symptoms for at least six months. Alternatively, a diagnosis of schizophreni-form disorder is used when patients have only experienced these symptoms between one and six months. Presumably, every schizophrenia patient was a candidate for a diagnosis of schizophreniform disorder, as it is basically the same thing as schizophrenia, only for a shorter period of time.

Delusional Disorder. People with delusional disorder endorse beliefs that are have no grounding in reality. Contrary to schizophrenia, however, delusional disorder is not marked by extreme behavior change or disorganized behavior. Patients with delusional disorder can function normally, except for their behaviors brought about by their delusions. An example of a common form of delusion seen in delusional disorder is erotomania.

Patients with erotomania believe that they are involved in a love affair with someone, even if this is not true. It is not uncommon for people with erotomania to believe they are having a relationship with a movie star or a famous politician.

Brief Psychotic Disorder. Brief psychotic disorder involves the sudden development of psychotic symptoms and rarely lasts for more than a few days. Typically, these episodes are brought about by an extremely stressful event,  such as the death or infidelity of a spouse or the loss of a job. After the psychotic symptoms remit, they rarely return and the person returns to normal. Brief psychotic disorder is very rare and not often seen in clinical settings.

Shared Psychotic Disorder.  Called folie a deux in French, shared psychotic disorder is perhaps the most puzzling of all these categories. Translated, folie a deux means “madness shared by two” and occurs when one person (let’s call this person A) has a close relationship with someone who has a delusion (person B). Over time, person A begins to believe in person B’s delusion and ultimately the two share the same delusion.

Drug-Induced Psychosis. Because the effects of some illegal drugs mimic psychotic symptoms, it is necessary to determine that a patient who is experiencing symptoms is not using drugs. Some drugs that can cause schizophrenia-like symptoms include cocaine, methamphetamine, and hallucinogens.

Heather Barnett Veague, Ph.D.
Heather Barnett Veague attended the University of California, Los Angeles, and received her Ph.D. in psychology from Harvard University in 2004. She is the author of several journal articles investigating information processing and the self in borderline personality disorder. Currently, she is the Director of Clinical Research for the Laboratory of Adolescent Sciences at Vassar College. Dr. Veague lives in Stockbridge, Massachusetts, with her husband and children.

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