Individuals with schizoid personality disorder may have particular difficulty expressing anger, even in response to direct provocation, which contributes to the impression that they lack emotion. Their lives sometimes seem directionless, and they may appear to ”drift" in their goals. Such individuals often react passively to adverse circumstances and have difficulty responding appropriately to important life events. Because of their lack of social skills and lack of desire for sexual experiences, individuals with this disorder have few friendships, date infrequently, and often do not marry. Occupational functioning may be impaired, particularly if interpersonal involvement is required, but individuals with this disorder may do well when they work under conditions of social isolation. Particu- larly in response to stress, individuals with this disorder may experience very brief psy- chotic episodes (lasting minutes to hours). In some instances, schizoid personality disorder may appear as the premorbid antecedent of delusional disorder or schizophre- nia. Individuals with this disorder may sometimes develop major depressive disorder.
Schizoid personality disorder most often co-occurs with schizotypal, paranoid, and avoid- ant personality disorders.
Schizoid personality disorder is uncommon in clinical settings. A prevalence estimate for schizoid personality based on a probability subsample from Part II of the National Co- morbidity Survey Replication suggests a prevalence of 4.9%. Data from the 2001—2002 3.1%.
solitariness, poor peer relationships, and underachievement in school, which mark these children or adolescents as different and make them subject to teasing.
Genetic and physiological. Schizoid personality disorder may have increased preva- lence in the relatives of individuals with schizophrenia or schizotypal personality disorder.
Individuals from a variety of cultural backgrounds sometimes exhibit defensive behaviors and interpersonal styles that may be erroneously labeled as ”schizoid.” For example, those who have moved from rural to metropolitan environments may react with ”emotional freezing” that may last for several months and manifest as solitary activities, constricted affect, and other deficits in communication. Immigrants from other countries are some- times mistakenly perceived as cold, hostile, or indifferent.
Schizoid personality disorder is diagnosed slightly more often in males and may cause more impairment in them.
Other mental disorders with psychotic Symptoms. Schizoid personality disorder can be distinguished from delusional disorder, schizophrenia, and a bipolar or depressive dis- order with psychotic features because these disorders are all characterized by a period of persistent psychotic symptoms (e.g., delusions and hallucinations). To give an additional diagnosis of schizoid personality disorder, the personality disorder must have been present before the onset of psychotic symptoms and must persist when the psychotic symptoms are in remission. When an individual has a persistent psychotic disorder (e.g., schizophre- nia) that was preceded by schizoid personality disorder, schizoid personality disorder should also be recorded, followed by ”premorbid" in parentheses.
Autism spectrum disorder. There may be great difficulty differentiating individuals with schizoid personality disorder from those with milder forms of autism spectrum disorder, behaviors and interests.
Personality change due to another medical condition. Schizoid personality disorder must be distinguished from personality change due to another medical condition, in which the traits that emerge are attributable to the effects of another medical condition on the central nervous system.
Substance use disorders. Schizoid personality disorder must also be distinguished from symptoms that may develop in association with persistent substance use.