Relationship among nightmare, insomnia and depression among residents in Japanese rural community

Abstract

Introduction Either nightmare or insomnia is known as independent factor associated with aggravation of depression. The aim of this community-based study was to clarify the relationship between the impacts of nightmare and insomnia on depressive status. Materials and methods This cross-sectional survey was conducted on residents in a rural community of Japan. A total of 2822 persons were eligible for this questionnaire survey including demographic variables, sleep hygiene related variables, the Pittsburgh Sleep Quality Index (PSQI) assessing the severity of insomnia, and a 12-item version of the Center for Epidemiological studies Depression scale (CES-D) manifesting the severity of depression. The frequency of nightmare was assessed with an item of nightmare on the PSQI. The total score of CES-D after excluding the insomnia item was used as the score of depression and that of PSQI after excluding the nightmare item was used as the score of insomnia. Results The result of multiple regression analysis revealed that both nightmare score and insomnia score were significantly associated with CES-D score (adjusted R2=0.18, p f A=0.09, p f A=0.39, p p fÅ 2=0.12). Post-hoc analysis revealed that the group with coexistence of nightmare and insomnia had significantly higher score than the healthy group ( p p p p p Conclusion Coexistence of nightmare and insomnia was thought to synergistically aggravate depressive symptom. Moreover, both nightmare and insomnia was thought to become a risk factor for the depression independently in the Japanese rural population. Acknowledgements We thank Kiyohisa Takahashi(Japan Foundation for Neuroscience and Mental Health) for helpful comments on the manuscript.