Data published in Clinical Psychological Science suggest that sleep deprivation may impair the ability to suppress intrusive thoughts. In a behavioral study that asked participants to suppress memories of emotionally negative or neutral scenes when given associated cues, those who were sleep deprived experienced significantly more memory intrusions. Such findings may have implications for psychiatric conditions characterized by “persistent, unwanted thoughts” such as obsessive-compulsive disorder, posttraumatic stress disorder, and major depressive disorder.
This study recruited 60 healthy individuals from the York area of England. Participants had no history of neurological, psychiatric, or sleep disorders. The study was divided into 2 sessions: (1) Session 1, completed in the evening; and (2) Session 2, completed the morning after an 8-hour delay.
Individuals were randomly assigned to the sleep (n=30) or sleep-deprivation (n=30) groups. Participants in the sleep group slept in the sleep laboratory during the 8-hour delay, while participants in the deprivation group remained awake.
Across both sessions, participants completed affect-evaluation and think/no think (TNT) tasks. Following a learning task during Session 1, in which participants were trained to associate certain face images with specific negative or neutral scenes, the TNT task during Session 2 presented the same facial images in red or green frames.
For red-framed faces (no-think trials), participants were asked to avoid thinking of the associated scene. For green-framed faces (think trials), participants were instructed to visualize the associated scene. Immediately after each face cue in the no-think trials, participants reported whether the associated scene had entered awareness on an ordinal scale: never, briefly, or often. Thought intrusion reports were compared between sleep groups.
Complete data were available for 59 participants. Mean age was 19.79 ± 1.63 years in the sleep group and 20.20 ± 1.75 years in the sleep deprivation group. Women comprised the majority of the total cohort (n=34; 57.6%). Overall intrusion scores were significantly higher for think compared to no-think trials, confirming the ability of participants to suppress thoughts when instructed (92.76% of think trials vs 28.87% of no-think trials; P <.001).
Sleep-deprived participants reported significantly more intrusions than well-rested individuals (P =.022), suggesting that sleep deprivation may affect memory control. Additionally, the sleep deprivation group experienced a 50% increase in intrusions between the mock TNT task performed during Session 1 and the true TNT task performed after the 8-hour delay. The sleep group did not experience significant changes in thought intrusions between sessions. In both groups, however, intrusions appeared to decrease across TNT trial blocks. Investigators hypothesized that repeated suppression of memories was “effective at stopping…[intrusions] on future trials.”
“Our findings indicate that sleep deprivation substantially increases people’s vulnerability to unwanted memories intruding into conscious awareness when they confront reminders,” the investigators wrote. These data may explain the apparent relationship between sleep deprivation and psychiatric disorders characterized by intrusive thoughts. Further studies are necessary to better understand the neurocognitive underpinnings of intrusion control.
Harrington MO, Ashton JE, Sankarasubramanian S, Anderson MC, Cairney SA. Losing control: sleep deprivation impairs the suppression of unwanted thoughts [published online October 15, 2020]. Clin Psychol Sci. doi: 10.1177/2167702620951511