A family history study evaluated first-degree relatives of 49 probands with degree relatives of probands with other somatoform disorders and affective disorder. The risk for a complicated medical history was 8.0% in the first-degree relatives of the somatization disorder probands, compared to 2.3% and 2.5% in the control groups (P < .01).
A family study of somatization disorder reported a significantly increased risk for the disorder among first-degree female relatives of somatization disorder probands (6.7%), compared to female relatives of control probands (2.4%). The study also reported an increased risk for antisocial personality disorder among the male (18.8%) and female (8.6%) relatives of the somatization disorder probands, compared to the risk in male (10.5%) and female (2.6%) relatives of control probands.
Twin studies have evaluated 14 MZ twin pairs and 21 DZ twin pairs in which one member had a somatoform disorder (including somatization disorder, conversion disorder, psychogenic pain disorder, and hypochondriasis). Of the MZ twin pairs, 29% were concordant for some type of somatoform disorder, compared to 10% of DZ twin pairs (not a significant difference in this small sample).
An analysis of a large Swedish adoption cohort identified a set of discriminant function variables that distinguished female adoptees with repeated brief sick leaves for somatic complaints and psychiatric disability (so-called somatizers) from other female adoptees. In a subsequent analysis, these somatizers were divided into two groups: high-frequency somatizers (those who had a high rate of psychiatric, abdominal, or back complaints) and diversiform somatizers (those who had a lower frequency of complaints but with multiple and highly variable symptoms). Of the high-frequency somatizers, 30% had histories of alcohol abuse or criminality (based on the national registries for these behaviors). Their male biological relatives were at increased risk for violent criminal behavior and alcohol abuse. For both types of somatizers, a cross- fostering analysis provided evidence for both congenital and postnatal influences on the development of the disorder.
These studies suggest a familial connection between some types of somatoform disorders and alcoholism and criminality.