Family studies in insomnia.

OBJECTIVE: Several predisposing factors to insomnia have been hypothesized, including a familial component; however, few studies have focused on this topic. The aim of this study is to evaluate the prevalence of insomnia among first-degree relatives of chronic insomniacs and to compare the symptoms between sporadic and familial insomnia.

METHODS: Two hundred fifty-six consecutive chronic insomniacs completed a clinical interview, psychometric questionnaires, a questionnaire on the family history of insomnia and, when indicated, a polysomnography. A control group was performed to estimate a base-rate incidence of insomnia in their families.

RESULTS: Patients with primary (n=77) and psychiatric (n=104) insomnia were definitely included. Of those with primary insomnia, 72.7% reported familial insomnia compared with 24.1% in the noninsomnia control group. Among the psychiatric insomniacs, 43.3% reported familial insomnia. The mother was the relative most frequently affected. Comparisons between the family prevalence rates of insomnia assessed by the probands and by first-degree relatives show high concordance. A tendency to a younger age at onset was observed in familial and primary insomnia.

CONCLUSION: This study reports a significant increase of familial aggregation of insomnia, warranting further genetic studies in primary insomnia with early age at onset.