Intrusive thoughts and their relationship to actigraphic measurement of sleep: towards a cognitive model of insomnia

Although cognitive over-arousal has been hypothesised as a causal factor in sleep-onset insomnia, relatively little is known about the specific pre-sleep intrusions which delay sleep. To investigate this relationship adequately 'live', verifiable, unobtrusive and independent monitoring of thought process and sleep pattern is essential. This study was designed with these requirements in mind. Voice-activated audiotape recordings of spontaneous thoughts, and actigraphic data from which to estimate sleep parameters, were obtained over three consecutive nights from 21 participants (63 subject nights). Content analysis of transcribed audiotapes yielded eight categories of pre-sleep intrusion. Results from correlational and regression analyses indicate that thinking about sleep and the anticipated consequences of poor sleep, along with general problem-solving are the strongest predictors of objective sleep latency. Principal Components Analysis suggests that intrusions can be subsumed under one of three factors: 'active problem-solving', 'present state monitoring' and 'environmental reactivity'. Implications for cognitive models and treatments of insomnia are discussed.