Some evidence suggests the cluster A personality<unk> s have shared genetic and environmental risk factors, and there is an increased prevalence of<unk>  in relatives of people with schizophrenia and schizotypal personality<unk> . Twin studies with<unk>  traits (e.g. low sociability and low warmth) suggest these are inherited. Besides this indirect evidence, the direct heritability estimates of SPD range from 50 to 59%. To Sula Wolff, who did extensive research and clinical work with children and teenagers with<unk>  symptoms,<unk>  personality has a constitutional, probably genetic, basis." The link between SPD and being underweight may also point to the involvement of biological factors. In general, prenatal caloric malnutrition, premature birth and a low birth weight are risk factors for being afflicted by mental<unk> s and may contribute to the development of<unk>  as well. Those who have experienced traumatic brain injury may be also at risk of developing features reflective of<unk> . Other historical researchers had hypothesized excessively perfectionist, unloving or neglectful parenting could play a role.
Schizoid personality disorder
Avoidant personality disorder
Histrionic personality disorder
Organic personality disorder
Haltlose personality disorder
Dependent personality disorder
Depressive personality disorder
Obsessive–compulsive personality disorder