On the moderating role of chronotype on the association between IQ and conscientiousness: the compensation effect occurs only in Evening-types

The mediating role of perceived social support in the relationship between morningness-eveningness and subjective well-being

Studies show that morningness preference and subjective well-being are positively related. However, little is known about potential factors that may underpin this association. In the present study, we explored the mediational role of general social support and its facets (family, friends, and significant other) in the relationship between morningness-eveningness and subjective well-being. The present study was conducted with a sample of 1,067 adults (51% women), with a mean (SD, range) age of 36.41 (9.95, 18-55) years. Our results corroborated earlier findings that morningness was positively associated with both subjective well-being and social support. Controlling for age and gender, we obtained significant mediation effects, showing that the association between morningness-eveningness and subjective well-being might stem, at least in part, from the higher levels of social support received by morning-oriented individuals. This may lead to the conclusion that social support is an important antecedent of the greater well-being reported by morning-oriented individuals.

The moderating role of personality traits in the relationship between chronotype and depressive symptoms

Due to the undeniably morning orientation of the social clock, the evening chronotype can be associated with negative consequences, both at the affective and cognitive levels. Evening-oriented individuals are more susceptible to affective disorders, show poorer educational achievements and consume stimulants more often than morning-oriented individuals. However, little is known about potential factors that may attenuate or amplify these negative emotional consequences of the evening preference. Thus, our aim was to examine whether personality traits interplay with chronotype in predicting depressive symptoms. We assessed the Big Five and the Big Two personality traits, morningness-eveningness and depressive symptoms in an online sample of 913 Polish individuals (468 females, 445 males), aged 18-35 (M = 26.34, SD = 5.15). Eveningness, higher neuroticism, lower conscientiousness and lower alpha-stability were associated with higher depressive symptoms. The magnitude of the association between eveningness and depressive symptoms decreased with higher conscientiousness and alpha-stability, as well as with lower neuroticism. In conclusion, high neuroticism, low conscientiousness and low alpha-stability increase the risk of depressive symptoms, particularly among evening chronotypes. The patients' chronotypes and personality traits should be taken into account in both the prevention and diagnostics of depression.

Circadian preference and intelligence - an updated meta-analysis

A large number of previous studies reported a link between circadian preference and psychometric intelligence with mixed results and various hypotheses about the source of this correlation. In this study, we aimed to update a previous meta-analysis about the correlation between circadian preference and intelligence. Our literature search identified a large number of new studies, resulting in an increase of over 100% in the number of studies and over 400% in the number of involved participants (total k = 30, total N = 11160) over the previous meta-analysis, sampling a much wider age range from children to adults in late middle age. Our meta-analysis revealed no significant link between morningness and intelligence (r = -0.008) when the entire sample was studied, and no evidence for publication bias. This overall effect, however, obscured the moderating effect of age. The morningness-intelligence correlation decreased with mean sample age (R² = 54%), ranging from a non-significant positive trend in children and adolescents to a significant negative correlation after young adulthood. Eveningness was positively correlated with intelligence (r = 0.056), but this finding is based on a more age-restricted sample and only reached significance with some model specifications. We hypothesize that the age-moderated correlation between circadian preference and intelligence reflects social effects, where more intelligent individuals are more able to adjust their daily schedules to their natural circadian rhythm.

The mediating effect of conscientiousness on the academic consequences of social jetlag

Social jetlag (SJL) causes impairment of academic achievement; on the other hand, the personality factor of conscientiousness is related to better grades. We evaluated the impact of conscientiousness on the academic consequences of social jetlag. Undergraduate students (n = 556) were evaluated throughout their first 3 years of university education. Conscientiousness, as a mediating factor in the structural equation modeling, explained 20% of the effect of SJL on academic achievement. This is the first cohort study to evaluate the mediating effect of personality on the consequences of SJL.