Place of chronic insomnia in the course of depressive and anxiety disorders

Abstract

Background: Insomnia is frequent in the general population and is often related to a psychiatric illness. However, little is known about how the chronicity of insomnia affects this relation and how often subjects with chronic insomnia have antecedents of psychiatric disorders. Methods: A total of 14,915 subjects aged from 15 to 100 years representative of the general population of the United Kingdom, Germany, Italy, and Portugal were interviewed by telephone using the Sleep-EVAL system. The questionnaire assessed current psychiatric disorders according to the DSM-IV classification and a series of questions assessed the psychiatric history. Insomnia was considered as chronic when it lasted for 6 months or more. Results: The prevalence for insomnia accompanied with impaired daytime functioning was 19.1% and significantly increased with age. More than 90% of these subjects had a chronic insomnia. About 28% of subjects with insomnia had a current diagnosis of mental disorders and 25.6% had a psychiatric history. A DSM-IV insomnia disorder was found in 6.6% of the sample. Presence of severe insomnia, diagnosis of primary insomnia or insomnia related to a medical condition, and insomnia that lasted more than one year were predictors of a psychiatric history. In most cases of mood disorders, insomnia appeared before (> 40%) or in the same time (> 22%) than mood disorder symptoms. When anxiety disorders were involved, insomnia appeared mostly in the same time (>38%) or after (> 34%) the anxiety disorder. Conclusions: The study shows that psychiatric history is closely related to the severity and chronicity of current insomnia. Moreover, chronic insomnia can be a residual symptom of a previous mental disorder and put these subjects to a higher risk of relapse.

Introduction

Insomnia is a distressing and disabling condition that affects up to one third of the general population. Epidemiological and clinical studies have shown that a high number of insomnia subjects also suffer from a concomitant mental disorder mainly depression or an anxiety disorder: between 40 and 60% of insomnia complainers fall into this category (Breslau et al., 1996, Buysse et al., 1994, Voleman et al., 1982, Ford and Kamerow, 1989, Hohagen et al., 1993, Mellinger et al., 1985, Ohayon, 1997, Ohayon et al., 1997a, Schramm et al., 1995, Tan et al., 1984). Retrospective studies that examined whether the insomnia resulted from a sleep disorder or was a symptom of some other mental disorder have shown that the insomnia is mostly an associated symptom of the mental disorder and does not warrant a separate diagnosis of insomnia (Ohayon, 1997).

However, how the chronicity of insomnia affects this relationship and how often chronic insomniac subjects have previously suffered from a mental disorder has been only minimally investigated. Results of longitudinal studies with individuals with insomnia suggested that the maintenance of insomnia problems over the time increases the likelihood of developing a concomitant mental disorder (Breslau et al., 1996, Hohagen et al., 1993, Ford and Kamerow, 1989). However, the past history of the subject was not specifically investigated in order to understand how chronic insomnia impacted psychiatric pathology.

In this perspective, we investigated the psychiatric history of insomniac subjects in the general population.