An exploration of pre-sleep cognitive activity in insomnia: imagery and verbal thought.

Abstract

Patients with insomnia commonly report that unpleasant intrusive thoughts and images prevent them falling asleep. Previous research has documented the topics people with insomnia think about during the pre-sleep period, but has not yet distinguished between different types of cognitive activity. Given that research relating to the anxiety disorders suggests that different types of cognitive activity, in particular images and verbal worry, are functionally independent, the present study aimed to provide a detailed phenomenological investigation of imagery and verbal thought in insomnia. A semi-structured interview, designed to assess the content and management of pre-sleep images and verbal thought, was administered to individuals with sleep-onset insomnia (N = 34) and good sleepers (N = 38) immediately following an afternoon nap. During the nap, heart rate and sleep-onset latency were measured objectively. The insomnia group was more likely than the good sleeper group to report negative images than positive images. The start, direction and stopping of pre-sleep images was rated as less controllable than pre-sleep verbal thoughts. Participants disengaged more from images compared with verbal thoughts, and the insomnia patients reported feeling less calm and relaxed at the end of the salient verbal thought compared with the good sleepers.