Daytime symptom patterns in insomnia sufferers: is there evidence for subtyping insomnia?

The type and severity of daytime symptoms reported by insomnia sufferers may vary markedly. Whether distinctive daytime symptom profiles are related to different insomnia diagnoses has not been studied previously. Using profile analysis via multidimensional scaling, we investigated the concurrent validity of ICSD-2 insomnia diagnoses by analysing the relationship of prototypical profiles of daytime symptoms with a subset of ICSD-2 diagnoses, such as insomnia associated to a mental disorder, psychophisiological insomnia, paradoxical insomnia, inadequate sleep hygiene, idiopathic insomnia, obstructive sleep apnea and restless legs syndrome. In a sample of 332 individuals meeting research diagnostic criteria for insomnia (221 women, M(age) =46 years.), the profile analysis identified four prototypical patterns of daytime features. Pearson correlation coefficients indicated that the diagnoses of insomnia associated to a mental disorder and idiopathic insomnia were associated with a daytime profile characterized by mood disturbance and low sleepiness; whereas the diagnoses of psychophysiological insomnia and inadequate sleep hygiene were related to a profile marked by poor sleep hygiene, daytime tension and low fatigue. Furthermore, whereas paradoxical insomnia was consistently associated to lower daytime impairment, insomnia associated to a mental disorder appeared as the most severe daytime form of insomnia. This classification of insomnia sufferers along multiple defining dimensions provides initial validation for two basic insomnia subtypes, with a presumably distinct aetiology: insomnia characterized mainly by an 'internal' component, and a 'learned' insomnia. Research to determine which dimensions are critical for inclusion or differential weighting for defining a general typological system for insomnia sufferers is warranted.