Unwanted memories often enter conscious awareness when individuals confront reminders. People vary widely in their talents at suppressing such memory intrusions; however, the factors that govern suppression ability are poorly understood. We tested the hypothesis that successful memory control requires sleep. Following overnight sleep or total sleep deprivation, participants attempted to suppress intrusions of emotionally negative and neutral scenes when confronted with reminders. The sleep-deprived group experienced significantly more intrusions (unsuccessful suppressions) than the sleep group. Deficient control over intrusive thoughts had consequences: Whereas in rested participants suppression reduced behavioral and psychophysiological indices of negative affect for aversive memories, it had no such salutary effect for sleep-deprived participants. Our findings raise the possibility that sleep deprivation disrupts prefrontal control over medial temporal lobe structures that support memory and emotion. These data point to an important role of sleep disturbance in maintaining and exacerbating psychiatric conditions characterized by persistent, unwanted thoughts. (Losing Control: Sleep Deprivation Impairs the Suppression of Unwanted Thoughts)
I don’t think this is wholly a bad thing. Unwanted thoughts are a part of the mind and need to be examined. Understanding, resolving, and finally extirpating unwanted thoughts is a very good thing if the process is wholesome and truthful. In this sense, a poor night’s sleep can be helpful by mildly forcing us to consider memories or thoughts we don’t want to be having but are. A similar reasoning applies to irritating tasks as they often force us to see how irritable we can be.