Epidemiology
SPD is uncommon in clinical settings and occurs slightly more commonly in males. It is rare compared with other personality disorders, with a prevalence estimated at less than 1% of the general population.
Philip Manfield suggests that SPD is far more common that is reported: "I believe that the schizoid condition is far more common... comprising perhaps as many as 40 percent of all personality disorders. This huge discrepancy is probably largely because someone with a schizoid disorder is less likely to seek treatment than someone with other axis-II disorders." Manfield backs this claim with a 1985 study by Valliant & Drake, who found that over 40% of a particular sample group of inner city males were schizoid.
Read more about this topic: Schizoid Personality Disorder