Impact of frequency of nightmares comorbid with insomnia on depression in Japanese rural community residents: a cross-sectional study.

OBJECTIVE

Nightmares and insomnia are known to be associated with the development and aggravation of depression. Our community-based study was conducted to clarify the relation between the impacts of nightmares and insomnia on depression.

METHODS

A cross-sectional questionnaire-based survey was administered to residents of a rural community in Japan. In all, 2822 participants responded to questions assessing personal characteristics, the Pittsburgh Sleep Quality Index (PSQI) for assessing insomnia, and a 12-item version of the Center for Epidemiological Studies Depression scale (CES-D) for evaluating depression. Nightmare frequency was assessed using an item for nightmares on the PSQI.

RESULTS

Nightmares more frequently occurred in participants with insomnia than those without (P < .01). Multiple regression analysis revealed that the scores of both nightmares and insomnia were significantly associated with the increase in depression score (nightmares (β = 0.09, P < .01); insomnia (β = 0.39, P < .01)). Participants with coexisting nightmares and insomnia showed higher depression scores than participants with insomnia alone or those with nightmares who did not have insomnia (P < .01).

CONCLUSIONS

Insomnia and nightmares independently and additively impact the aggravation of depression.