Particularly in response to stress, individuals with this disorder may experience transient psychotic episodes (lasting minutes to hours), although they usually are insufficient in du- ration to warrant an additional diagnosis such as brief psychotic disorder or schizophreni- form disorder. In some cases, clinically significant psychotic symptoms may develop that meet criteria for brief psychotic disorder, schizophreniform disorder, delusional disorder, or schizophrenia. Over half may have a history of at least one major depressive episode.
From 30% to 50% of individuals diagnosed with this disorder have a concurrent diagnosis of major depressive disorder when admitted to a clinical setting. There is considerable co- occurrence with schizoid, paranoid, avoidant, and borderline personality disorders.
In community studies of schizotypal personality disorder, reported rates range from 0.6% in Norwegian samples to 4.6% in a U5. community sample. The prevalence of schizotypal personality disorder in clinical populations seems to be infrequent (0%—1.9%), with a higher estimated prevalence in the general population (3.9%) found in the National Epi- demiologic Survey on Alcohol and Related Conditions.
Schizotypal personality disorder has a relatively stable course, with only a small propor- tion of individuals going on to develop schizophrenia or another psychotic disorder.
solitariness, poor peer relationships, social anxiety, underachievement in school, hyper- sensitivity, peculiar thoughts and language, and bizarre fantasies. These children may ap- pear ”odd” or ”eccentric” and attract teasing.
Genetic and physiological. Schizotypal personality disorder appears to aggregate fa- milially and is more prevalent among the first-degree biological relatives of individuals with schizophrenia than among the general population. There may also be a modest in- crease in schizophrenia and other psychotic disorders in the relatives of probands with schizotypal personality disorder.
Cognitive and perceptual distortions must be evaluated in the context of the individual’s cultural milieu. Pervasive culturally determined characteristics, particularly those regard- ing religious beliefs and rituals, can appear to be schizotypal to the uninformed outsider (e.g., voodoo, speaking in tongues, life beyond death, shamanism, mind reading, sixth sense, evil eye, magical beliefs related to health and illness).
Schizotypal personality disorder may be slightly more common in males.
Other mental disorders with psychotic symptoms. Schizotypal personality disorder can be distinguished from delusional disorder, schizophrenia, and a bipolar or depressive disorder with psychotic features because these disorders are all characterized by a period of persistent psychotic symptoms (e.g., delusions and hallucinations). To give an addi- tional diagnosis of schizotypal personality disorder, the personality disorder must have been present before the onset of psychotic symptoms and persist when the psychotic symptoms are in remission. When an individual has a persistent psychotic disorder (e.g., schizophrenia) that was preceded by schizotypal personality disorder, schizotypal per- sonality disorder should also be recorded, followed by ”premorbid" in parentheses.
Neurodevelopmental disorders. There may be great difficulty differentiating children with schizotypal personality disorder from the heterogeneous group of solitary, odd chil- dren whose behavior is characterized by marked social isolation, eccentricity, or peculiar- ities of language and whose diagnoses would probably include milder forms of autism spectrum disorder or language communication disorders. Communication disorders may be differentiated by the primacy and severity of the disorder in language and by the char- acteristic features of impaired language found in a specialized language assessment.
Milder forms of autism spectrum disorder are differentiated by the even greater lack of so- cial awareness and emotional reciprocity and stereotyped behaviors and interests.