The attempted suppression of presleep cognitive activity in insomnia

This study investigated the effects of attempted thought suppression during sleep initiation in the maintenance of sleep-onset insomnia. Insomniacs (N = 30) and good sleepers (N = 30) selected the thought most likely to dominate their presleep cognitive activity. Participants were randomly allocated to either a suppression or nonsuppression condition. The former group were instructed to suppress the self-selected thought during the presleep period, whereas the latter group were instructed not to control their thoughts but rather to relax and let thoughts come and go. Participants instructed to suppress estimated their sleep-onset latency to be longer and their sleep quality to be poorer than did participants given nonsuppression instructions. This effect was observed across diagnostic status.