DENVER—A reciprocal relationship may exist between generalized anxiety disorder and insomnia, according to a Canadian study presented at the 19th Annual Meeting of the Associated Professional Sleep Societies. “It is often assumed in clinical practice that insomnia is a symptom that will subside with remission of the comorbid psychiatric condition. However, there is also evidence suggesting insomnia can actually increase the risk of relapse,” reported Charles M. Morin, PhD, who is a Professor of Psychology at the Université Laval, Quebec.

Dr. Morin’s research team sought to document the prevalence of both insomnia symptoms and syndromes in individuals meeting DSM-IV criteria for generalized anxiety disorder. “We were also interested in examining the relationship between insomnia and generalized anxiety disorder and assessing the risks associated with insomnia,” he said.

At baseline, 1,362 randomly selected participants were enrolled in the population-based study. Individuals 18 or older who responded to an initial telephone survey and were willing to respond to self-report questionnaires every six months for two years were included. Of those enrolled, 956 persons remained in the study, after exclusion of those who had sleep disorders other than insomnia. Study participants also completed the Worry and Anxiety Questionnaire to assess whether they had generalized anxiety disorder.

The study cohort was categorized into three groups: those who were good sleepers and did not complain of insomnia; those who had insomnia symptoms; and those who had a full-blown insomnia syndrome, based on insomnia symptoms, duration, and frequency.

Analyzing data only from baseline and the six-month time point, the investigators found that those with generalized anxiety disorder had a significantly higher prevalence of insomnia both in terms of symptoms and syndromes. Overall, nearly twice as many patients with generalized anxiety disorder at baseline had insomnia symptoms or syndrome at six months compared with those without generalized anxiety disorder. Additionally, insomnia syndrome was three times more prevalent in the participants with generalized anxiety disorder than in those without it at baseline.

The researchers also studied patients who still had generalized anxiety disorder at the six-month follow-up. Those who had generalized anxiety disorder at baseline were nine times more likely to continue presenting with the disorder at follow-up, and patients with insomnia were four times more likely to develop generalized anxiety disorder than were those who were good sleepers. “That in itself is strongly suggestive that insomnia is a risk factor for subsequent generalized anxiety disorder even if there is no evidence [of generalized anxiety disorder] at baseline,” commented Dr. Morin.

“The main implication is that insomnia should be attended to, particularly if it is a syndrome, because it may bring about something else. It should also not always be strictly assumed that it will go away if you treat the underlying condition,” Dr. Morin said.

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—Michelle Stephenson

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