A 2011 study on suicidal inpatients at a Moscow hospital found that schizoids were the least common patients, while those with cluster B personality disorders were the most common. Asperger syndrome
Several studies have reported an overlap or comorbidity with the autism spectrum disorder Asperger syndrome. Asperger syndrome had traditionally been called "schizoid disorder of childhood", and Eugen Bleuler coined both the terms "autism" and "schizoid" to describe withdrawal to an internal fantasy, against which any influence from outside becomes an intolerable disturbance. In a 2012 study of a sample of 54 young adults with Asperger syndrome, it was found that 26% of them also met criteria for SzPD, the highest comorbidity out of any personality disorder in the sample (the other comorbidities were 19% for obsessive–compulsive personality disorder, 13% for avoidant personality disorder and one female with schizotypal personality disorder). Additionally, twice as many men with Asperger syndrome met criteria for SzPD than women. While 41% of the whole sample were unemployed with no occupation, this rose to 62% for the Aspergers and SzPD comorbid group. Tantam suggested that Asperger syndrome may confer an increased risk of developing SzPD. A 2019 study found that 54% of a group of males aged 11 to 25 with Asperger syndrome showed significant SzPD traits, with 6% meeting full diagnostic criteria for SzPD, compared to 0% of a control.In the 2012 study, it was noted that the DSM may complicate diagnosis by requiring the exclusion of a pervasive developmental disorder (PDD) before establishing a diagnosis of SzPD.
He described these personalities as "comfortably dull and at the same time sensitive, people who in a narrow manner pursue vague purposes".In 1910, August Hoch introduced a very similar concept called the "shut-in" personality. Characteristics of it were reticence, seclusiveness, shyness and a preference for living in fantasy worlds, among others. In 1925, Russian psychiatrist Grunya Sukhareva described a "schizoid psychopathy" in a group of children, resembling todays SzPD and ASD. About a decade later Pyotr Gannushkin also included Schizoids and Dreamers in his detailed typology of personality types.Studies on the schizoid personality have developed along two distinct paths. The "descriptive psychiatry" tradition focuses on overtly observable, behavioral and describable symptoms and finds its clearest exposition in the DSM-5. The dynamic psychiatry tradition includes the exploration of covert or unconscious motivations and character structure as elaborated by classic psychoanalysis and object-relations theory. The descriptive tradition began in 1925 with the description of observable schizoid behaviors by Ernst Kretschmer. He organized those into three groups of characteristics:
Unsociability, quietness, reservedness, seriousness and eccentricity. Timidity, shyness with feelings, sensitivity, nervousness, excitability, fondness of nature and books. Pliability, kindliness, honesty, indifference, silence and cold emotional attitudes.These characteristics were the precursors of the DSM-III division of the schizoid character into three distinct personality disorders: schizotypal, avoidant and schizoid. Kretschmer himself, however, did not conceive of separating these behaviors to the point of radical isolation but considered them to be simultaneously present as varying potentials in schizoid individuals.