Investigating racing thoughts in insomnia: A neglected piece of the mood-sleep puzzle?

Cognitive arousal is thought to play a key role in insomnia disorder. However, although patients frequently complain about racing thoughts appearing at bedtime, studies have considered 'cognitive arousal' as a synonym of rumination and worry, but not as racing thoughts per se. The latter have been mainly linked to hypomanic/manic episodes of bipolar disorder (BD). Here we aimed at investigating self-reported racing thoughts in insomnia disorder, and their specific contribution to insomnia severity, as compared to worry and rumination.

72 adults with insomnia disorder, 49 patients with BD in a hypomanic episode and 99 healthy individuals completed the Racing and Crowded Thoughts Questionnaire (RCTQ). Mood symptoms were assessed in patients with insomnia disorder.

RCTQ scores were overall higher in insomnia disorder, especially in sleep-onset insomnia, compared to the hypomanic and healthy groups. Moreover, racing thoughts showed an increase in the evening and at bedtime in sleep-onset insomnia. Importantly, racing thoughts at bedtime, but not rumination and worry, were associated with insomnia severity.

Our results are the first to show that racing thoughts is a transdiagnostic symptom in mood and sleep disorders. Racing thoughts, not only rumination and worry, might contribute to the maintenance of sleep difficulties in insomnia. Clinical trials' registration number: NCT04752254.