A twin-study of genetic contributions to morningness–eveningness and depression

Abstract

Circadian rhythms are associated with the preference for sleep–wake timing, also known as morningness–eveningness (ME). Both circadian rhythms and ME are influenced by genetic factors. Studies show an association between eveningness and depression. This study investigates the heritability of ME and whether ME and depression share common genetic influences. Study participants (n = 1237) were from the Vietnam Era Twin Study of Aging, a longitudinal study of aging with a baseline in midlife. Participants received the Morningness–Eveningness Questionnaire (MEQ) and the Center for Epidemiologic Studies Depression (CES-D) Scale as part of an extensive neurocognitive and psychosocial assessment. MEQ correlations between members of twin pairs were 0.41 (95% CI 0.31–0.49) for monozygotic (MZ) twins and 0.28 for dizygotic (DZ) twins (95% CI 0.19–0.41). CES-D correlations were 0.38 (95% CI 0.28–0.46) for MZ twins and 0.24 (95% CI 0.14–0.36) for DZ twins. Greater eveningness (i.e. lower MEQ scores) was significantly related to more depression symptoms (phenotypic correlation = −0.15 (95% CI −0.21 to −0.09). In the best fitting model, the heritability estimates are 0.42 for the MEQ and 0.37 for the CES-D. A significant genetic correlation of −0.21 indicated that ME and depression share a significant amount of their underlying genetic variance. The genetic covariance between ME and depression accounted for 59.1% of the phenotypic correlation. Of the CES-D sub-scales, Depressed Mood and Interpersonal Difficulties were significantly heritable, while only Well-Being had a significant genetic correlation with ME. ME and depression are both heritable (ME 0.42, depression 0.37) and share common genetic factors, suggesting an overlap in etiology and the relevance of circadian rhythms to depression. Further study of this relationship may help elucidate etiological factors in depression and targets for treatment.

• Circadian rhythms
• depression
• diurnal preference
• morningness–eveningness
• genetic
• twin studies
• VETSA

Acknowledgements

The authors gratefully acknowledge the continued cooperation and participation of the members of the VET Registry and their families. Without their contribution this research would not have been possible. We also appreciate the time and energy of many staff and students on the VETSA projects.

Declaration of Interest

This work was supported by National Institute on Aging Grants R01 AG018386, AG022381, and AG022982 (to William S. Kremen), R01 AG018384 (to Michael J. Lyons). This material was, in part, the result of work supported with resources of the VA San Diego Center of Excellence for Stress and Mental Health Healthcare System. The content is solely the responsibility of the authors and does not necessarily represent official views of the NIA, NIH, or VA. The Cooperative Studies Program of the U.S. Department of Veterans Affairs provided financial support for development and maintenance of the Vietnam Era Twin Registry.