The cause of personality disorders isn't known. Biologic theorists believe that chromosomal or nervous system disorders are causes. Social theorists believe learned behavior responses cause the disorders. Psychodynamic theorists use deficiencies in ego development to explain causes.
Those with schizoid personality disorder do not have schizophrenia, but it is thought that many of the same risk factors in schizophrenia may cause schizoid personality disorder. Relatives are not thought to be at risk for developing this disorder.
The following research may in part be applicable to causes of schizoid personality disorder:
The cause of schizophrenia has yet to be determined, although research suggests the interaction of genetic endowment and major environmental upheaval during development of the brain. Lines of research involving genetic studies and evidence for neurodevelopmental disruption are starting to converge: neurodevelopmental disruption may be the result of genetic and, or, environmental stressors early in development, leading to subtle alterations in the brain. Environmental factors later in development can either exacerbate or ameliorate expression of genetic or neurodevelopmental defects. The onset and course of schizophrenia are most likely the result of an interaction between genetic and environmental influences.
