Merck Manual

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Introduction to Schizophrenia and Related Disorders


Carol Tamminga

, MD, UT Southwestern Medical Dallas

Reviewed/Revised Apr 2022 | Modified Sep 2022
Topic Resources

Schizophrenia Schizophrenia Schizophrenia is characterized by psychosis (loss of contact with reality), hallucinations (false perceptions), delusions (false beliefs), disorganized speech and behavior, flattened affect... read more and related psychotic disorders— brief psychotic disorder Brief Psychotic Disorder Brief psychotic disorder consists of delusions, hallucinations, or other psychotic symptoms for at least 1 day but < 1 month, with eventual return to normal premorbid functioning. Brief psychotic... read more , delusional disorder Delusional Disorder Delusional disorder is characterized by firmly held false beliefs (delusions) that persist for at least 1 month, without other symptoms of psychosis. Delusions are distinguished from mistaken... read more , schizoaffective disorder Schizoaffective Disorder Schizoaffective disorder is characterized by psychosis, other symptoms of schizophrenia, and significant mood symptoms. It is differentiated from schizophrenia by occurrence of ≥ 1 episode of... read more , schizophreniform disorder Schizophreniform Disorder Schizophreniform disorder is characterized by symptoms identical to those of schizophrenia but that last ≥ 1 month but < 6 months. Psychosis refers to symptoms such as delusions, hallucinations... read more , and schizotypal personality disorder Schizotypal Personality Disorder (STPD) Schizotypal personality disorder is characterized by a pervasive pattern of intense discomfort with and reduced capacity for close relationships, by distorted cognition and perceptions, and... read more —are characterized most prominently by psychotic symptoms and often by negative symptoms and cognitive dysfunction.

Psychotic symptoms include delusions, hallucinations, disorganized thinking and speech, and bizarre and inappropriate motor behavior (including catatonia).

Negative symptoms refer to a decrease in or lack of normal emotions and behaviors, such as having a flattened affect and lack of motivation.

Cognitive dysfunction in these disorders affects attention, executive function, and memory.

Diagnosis is based on symptoms and the course of the illness; biologic markers of the disease have not yet been identified, but they are widely sought.

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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