Previous findings suggest that personality traits and dysfunctional sleep-related cognitions may perpetuate insomnia, but findings concerning this have been scarce. Thus, we hypothesized that personality and sleep-related cognitions influence the severity of insomnia, and investigated the association personality and sleep-related cognitions had with various sleep-related parameters, including severity of insomnia. Forty-four patients with psychophysiological insomnia were assessed using The Temperament and Character Inventory, the Insomnia Severity Index, the Pittsburgh Sleep Quality Index, the Epworth Sleepiness Scale, the Dysfunctional Belief and Attitudes toward Sleep Scale, the Pre-Sleep Arousal Scale and the Hospital Anxiety and Depression Scale. Insomnia severity was significantly and positively correlated with harm avoidance, self-transcendence and sleep-related cognitions, and negatively correlated with novelty seeking, reward dependence, and cooperativeness. Dysfunctional sleep-related cognitions were positively correlated with insomnia severity and sleep quality. Stepwise multiple regression analysis showed that sleep-related cognitions, depression and reward dependence scores were significant determinants of insomnia severity, and that sleep-related cognitions and self-transcendence were significant positive determinants of sleep quality. Reward dependence, depression and sleep-related cognitions were associated with insomnia severity, and comparison with previous findings implied that 'internalizing behavior' and depression may be more plausible candidates for the link between personality and insomnia than anxiety. Considering the major role of cognitive-behavioral treatment (CBT) in the treatment of insomnia, assessment of these factors and management of sleep-related cognitions may help alleviate symptoms in patients with insomnia.
