Purpose: Researchers have proposed that multiple factors such as hyperarousal, conditioning, worrying, or cortical arousal play roles in the predisposition to, initiation, and perpetuation of insomnia disorder. Previously, only a few studies investigated the differential effects of intrusive visual imagery (IVI) and intrusive verbal thoughts (IVT) on pre-sleep arousal or insomnia severity. The aim of the current cross-sectional study was to examine these effects as well as the moderator role of visual imagery ability (VIA) on the relationship between IVI and pre-sleep arousal.

Methods: A path model comprising the variables of IVI, IVT, pre-sleep arousal, and insomnia severity was tested with 166 of 1444 participants (M_age = 25.5, SD = 5.26) who were identified as having insomnia disorder based on a 12-question form corresponding to DSM-5 criteria for insomnia disorder and Insomnia Severity Index scores (≥ 8). The moderator role of VIA on the relationship between IVI and pre-sleep arousal was evaluated with a moderation analysis.

Results: It was found that IVI (β = 0.44, p < .001), but not IVT (β = 0.15, p = .12), significantly predicted pre-sleep arousal and pre-sleep arousal (β = 0.44, p < .001) significantly predicted insomnia severity. In addition, the indirect effect of IVI via pre-sleep arousal (IE = 0.19, p < .001) on insomnia severity was significant. Finally, the moderator role of VIA on the relationship between IVI and pre-sleep arousal (p = .07) was not significant.

Conclusions: IVI may play a more important role in insomnia disorder than IVT. Interventions targeting pre-sleep visual imagery can help poor sleepers alleviate insomnia severity.