Two studies examined the link between sleep quality and conspiracy theory beliefs, as well as the underlying mechanisms. In Study 1 (n = 540), participants with poorer sleep quality over the past month reported higher conspiracy beliefs about the 2019 Notre Dame fire when exposed to Notre Dame fire conspiracy theories compared to non-conspiracy information. Study 2 (n = 575) investigated the underlying psychological mechanisms connecting poor sleep quality with increased conspiracy beliefs and whether insomnia shows a similar pattern. We found that poorer sleep quality and insomnia were positively correlated with conspiracy theory beliefs – conspiracy mentality and belief in specific conspiracy theories. A consistent indirect effect through depression was uncovered, although there were inconsistent indirect relationships between both sleep quality and insomnia with conspiracy beliefs for anger and paranoia. These findings suggest that improving sleep quality could reduce susceptibility to conspiracy theories, highlighting the need for sleep-focussed interventions.
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