LAUSR

Patients with clinical insomnia commonly report intrusive thinking (IT) as a common contributor to delayed sleep onset. Evidence suggests that the default mode network (DMN) may contribute to this intrusive thinking. Therefore, we employed continuous theta burst (cTBS) repetitive transcranial magnetic stimulation (rTMS) to modulate DMN activation, and thus reduce IT before sleep. In a counterbalanced cross-over design, active or sham cTBS was administered to 20 participants with clinical insomnia, 8 males (Mage=31.63, SD=6.74) and 12 females (Mage=23.75, SD=4.29), with sessions separated by at least 5 days. To assess intrusive thoughts prior to sleep, participants took the Glasgow Content of Thoughts Inventory (GCTI). We utilized the subscale of the GCTI measuring sleep and wakefulness. Higher scores indicate more persistent intrusive thoughts. We conducted a mixed ANOVA to examine effects of sham and active cTBS conditions on intrusive thoughts. There was a medium effect size (ηp2 =.087) but no significant variance (p>.05) in average IT scores between participants sham cTBS (M=19.100, SD=5.349) and active cTBS (M=18.200, SD=4.502) Post-TMS sessions. There was a significant interaction between sex, TMS, and administration (F(1,18)= 4.697; ηp2=.207; p=.044). We then conducted a simple effects analysis between males and females. There was no significant effect of cTBS condition on reported intrusive thinking post-TMS administration (F(1,7)= .628; ηp2=.082; p=.454). However, there was a significant interaction of cTBS condition on intrusive thoughts post-TMS administration for females (F(1,11)= 5.894; ηp2=.349; p=.034). Post-hoc pairwise comparison revealed that females reported significantly greater intrusive thinking post-TMS administration (M=20.167, SD=5.68) compared to pre-TMS administration (M=17.5, SD=5.73) during their sham cTBS session (p=.042). This was not present post-TMS administration during active cTBS (p>.05). There was a decrease in intrusive thoughts relating to sleep and wakefulness in females, but not males, following active TMS. Interestingly, we also observed an increase in intrusive thoughts for the sham condition, suggesting that participants may have developed expectations of improvement and been sensitized to these cognitions when sleep was not improved. These findings are encouraging suggesting that cTBS may improve IT, although preliminary data suggest this may differ between males and females. W81XWH2010173