Contents lists available at ScienceDirect Psychiatry Research journal homepage: www.elsevier.com/locate/psychres Associations of depression and seasonality with morning-evening preference: Comparison of contributions of its morning and evening components Arcady A. Putilov ⁎ Research Institute for Molecular Biology and Biophysics, Novosibirsk, Russia ARTICLE INFO Keywords: Morningness-eveningness Chronotype Sleep-wake pattern Seasonal affective disorder Anxiety Somatization Health ABSTRACT Despite predominance of positive findings on associations of morning-evening preference with seasonality and depression, it remains to be clarified whether morning and evening components of this preference equally contribute to these associations and whether these associations persist after accounting for confounding vari- ables. Data on retrospectively reported seasonal changes in well-being, mood, and behaviors were collected from 2398 residents of West Siberia, South and North Yakutia, Chukotka, Alaska, and Turkmenistan. Other self- reports included mental and physical health, sleep duration, and adaptabilities of the sleep-wake cycle. Depression was found to be linked to morning rather than evening component of morning-evening preference, i.e., morning lateness. Morning lateness was also linked to retrospectively reported degree of seasonal changes rather than to severity of problems associated with such changes. Variation in morning-evening preference explained not more than 2% and 4% of the total variation in depression and seasonality, respectively. The associations became even weaker but remained significant after accounting for other differences between re- spondents, such as their gender, age, physical health, and adaptability of their sleep-wake cycle. These results have practical relevance for understanding of the roles playing by morning earliness and insensitivity to seasonal changes in the environment to protection against different mood disorders. 1. Introduction Seasonality and morning-evening preference represent two major domains of individual differences in adaptation of human mood, be- havior and physiology to annual and diurnal changes in the natural and social environment. As early as in the end of the 19th century, Emil Kraepelin and his students have recognized that psychiatric disorders can be associated with evening preference and certain seasons of the year (see Becker et al. (2016), and Wehr (1989), respectively, for more details). A modern search for possibility of such associations has been initiated by description of the so-called Seasonal Affective Disorder (SAD) and beneficial results of its treatment with morning and evening bright light (Rosenthal et al., 1984b). A condition characterized by re- occurrence of depressive episodes in winter (winter depression or SAD of winter type) was related to a delayed circadian phase (Lewy et al., 1987) and to seasonal changes in availability of bright light in the early morning and late evening hours (Rosenthal et al., 1984b). Such at- tempts to consider winter depression in the theoretical framework of chronobiology led to prediction that depression is significantly linked to morning-evening preference and seasonality. Seasonality is defined as individual's tendency to annual mood and behavioral variation, and it is often self-assessed retrospectively with the Seasonal Pattern Assessment Questionnaire or SPAQ (Rosenthal et al., 1984a). It was demonstrated that higher self-reported level of depression significantly correlated with higher amplitude of retro- spectively reported seasonal changes (Putilov et al., 1994, 1999; Oyane et al., 2008). Moreover, higher seasonal fluctuations throughout sea- sons were related to mood disorders (Brambilla et al., 2012; Hakkarainen et al., 2003), evening preference (e.g., Baek et al., 2016; Murray et al., 2003; Zhang et al., 2015), and delayed sleep phase syndrome (Lee et al., 2011). However, negative findings were also re- ported. In the study of Natale et al. (2005), evening preference was found to correlate with seasonality scale in Italian but not Spanish sample. Moreover, Oginska and Oginska-Bruchal, (2014) did not reveal significant relationship between the SPAQ seasonality scale and a morning-evening preference. Based on morning-evening preference people can be divided into chronotypes with different sleep-wake patterns (Kerkhof, 1998; Adan et al., 2012) and this preference is usually scored with unidimensional questionnaire instruments, such as the 19-item scale for self-assessment http://dx.doi.org/10.1016/j.psychres.2017.09.054 Received 18 January 2017; Received in revised form 17 April 2017; Accepted 22 September 2017 ⁎ Correspondence address: 11, Nipkowstr., 12489 Berlin, Germany. E-mail address: putilov@ngs.ru. Psychiatry Research xxx (xxxx) xxx–xxx 0165-1781/ © 2017 Elsevier B.V. All rights reserved. Please cite this article as: Putilov, A.A., Psychiatry Research (2017), http://dx.doi.org/10.1016/j.psychres.2017.09.054