Family study of fibromyalgia and affective spectrum disorder.

BACKGROUND: Fibromyalgia is one member of a proposed group of psychiatric and medical disorders, collectively termed affective spectrum disorder (ASD), hypothesized to share possibly heritable pathophysiologic features. Two predictions of the ASD hypothesis were tested: ASD, taken as a single entity, aggregates in families; and fibromyalgia coaggregates with other forms of ASD in families.
METHODS: Probands with and without fibromyalgia, together with their first-degree relatives, were administered structured diagnostic interviews. Noninterviewed relatives were diagnosed according to information provided by interviewed relatives. Aggregation and coaggregation of disorders were analyzed with proband predictive logistic and linear regression models.
RESULTS: In 533 relatives of 78 probands with fibromyalgia and 272 relatives of 40 probands without fibromyalgia, the estimated odds ratio (OR) (95% confidence interval) for the familial aggregation of ASD was 1.8 (.97, 3.2), p = .065, and the increase in number of forms of ASD in a relative for each additional form of ASD in a proband was .076 (.027, .1240), p = .002. The OR for the coaggregation of fibromyalgia with other forms of ASD was 2.0 (1.2, 3.2), p = .004; this remained significant even after excluding all mood-disorder diagnoses: 1.8 (1.1, 3.0), p = .012.
CONCLUSIONS: These findings support familial aggregation of ASD collectively and familial coaggregation of fibromyalgia with other forms of ASD.