Insomnia Is a Common Complaint in the General Population.1 the Diagnosis of Insomnia Involves

1739 INSOMNIA IS A COMMON COMPLAINT IN THE GENERAL POPULATION.1 THE DIAGNOSIS OF INSOMNIA INVOLVES BOTH SLEEP SYMPTOMS, SUCH AS DIFFICULTY INITIATING or maintaining sleep, and daytime symptoms, including fatigue, mood disturbance, and cognitive impairment. Insomnia may represent a transient problem triggered by specific life events, or, in contrast, it may also follow a chronic course due to the presence of both predisposing and perpetuating factors. Several risk factors have been hypothesized in chronic insomnia such as age, sex, education, marital and work status, behavioral and environmental factors, and the presence of mental or medical disorders.2-8 However, little is known regarding the existence and influence of family history. Three studies have focused on this topic, and all suggest the potential involvement of a familial component in insomnia. One study found that 55% of individuals with childhood-onset and 39% of those with adulthood-onset insomnia reported at least 1 family member with sleep problems.9 However, the sample size was small (N = 56), the results were based on only 1 dichotomous (yes/no) question, and information was lacking on which relative was affected and by which sleep problem. In another study of 285 patients consulting for insomnia, 26.7% reported at least 1 family member with insomnia, and there were trends suggesting higher rates of family history of insomnia among patients with an earlier age of onset of insomnia.10 Finally, a recent study reported that a family history of insomnia was more prevalent among individuals with primary insomnia (72.7%) than among those with insomnia comorbid with a psychiatric disorder (43.3%) and healthy controls (23.5%).11 In summary, the available evidence is derived from relatively small samples composed of clinical patients attending a sleep clinic, and only 1 study used a control group.11 Several twin studies strongly suggest that genetic factors influence insomnia. Among those studies, the genetic effects accounted for approximately one third of the variance in insomnia complaints.12-14 Moreover, family history of insomnia seems to be more likely in cases of early onset of the condition.14 A genetic predisposition has also been established for normal sleep and for most other sleep disorders.15 Except for the rare fatal familial insomnia,16,17 only 1 genetic case study has been reported in literature, with a beta3 GABA(A) receptor mutation in a patient affected with a chronic familial insomnia.18 The presence of putative biologic factors needs to be discovered, with indication of different factors affecting early and late onset of insomnia. Due to a possible intermittent mode of entry in insomnia, the age of onset is not always easy to ascertain. In addition, transient insomnia may occur only in the presence of specific triggering factors. The Family History of Insomnia in a Population-Based Sample