Background: Emerging data suggested a significant familial aggregation of insomnia. We aimed to clarify the familial aggregation and heritability of insomnia disorder by using structural clinical interviews for the ascertainment of insomnia and psychiatric disorders in a community-based sample.
Methods: Seventy-five adolescents with insomnia and their 180 first degree relatives, together with 141 age- and sex-matched non-insomnia controls and their 382 first degree relatives, were recruited. Each subject underwent a structured clinical interview and completed a series of psychometric inventories. The rates of insomnia disorder among the first degree relatives were employed to analyze familial aggregation. Heritability of insomnia was analyzed by SOLAR program as based on father-mother-offspring trios.
Results: Our study confirmed a significant familial aggregation of insomnia with a first degree relatives' recurrence risk of 2.33 for current insomnia and 2.82 for lifetime insomnia, respectively. The heritability±SE of current and lifetime insomnia disorder was 0.48±0.13 and 0.61±0.11 (p<0.001), respectively, which were higher than insomnia symptoms as estimated by the Insomnia Severity Inventory (h(2)±SE=0.27±0.09) and the Pittsburgh Sleep Quality Index (h(2)±SE=0.30±0.11). After exclusion of comorbid psychiatric disorders, the heritability for current and lifetime primary insomnia was 0.45±0.17 (p=0.007) and 0.58±0.21 (p=0.004), respectively.
Conclusions: Our study demonstrates a significant familial aggregation with a high heritability of insomnia disorder. The strong heritability of insomnia persists despite the exclusion of psychiatric disorders. Further molecular genetic investigation of insomnia is indicated.
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