Chronotype and psychopathology: insights from a genetically informative design.

Study objectives: Chronotype has been linked to a wide variety of psychiatric conditions. In particular, evening chronotype could be a transdiagnostic risk factor for different mental health difficulties. In this study we examine how chronotype relates to psychopathology and whether it can be conceptualised as part of the global construct of psychopathology (p-factor) by studying the genetic and environmental overlap between these variables. We utilise data from a genetically informative design to study: 1) the association between chronotype and psychopathology; 2) the genetic and environmental overlap between chronotype and psychopathology; and 3) the predictive value of polygenic score (PGS) for chronotype for psychopathology.

Methods: Chronotype was measured using an abbreviated version of the Munich Chronotype Questionnaire. Measures of psychopathology included: depression, anxiety, alcohol use and psychotic experiences among others. We used different psychopathology and chronotype-related polygenic scores. Association between chronotype and psychopathology were examined with three approaches: 1) phenotypic associations; 2) genetic and environmental associations using the twin design, and 3) genetic associations using PGS.

Results: There were small, though largely significant, associations between chronotype and psychopathology with significant genetic and environmental overlap. Chronotype PGS significantly predicted a very small proportion of the variance for some measures of psychopathology (e.g., symptoms of ADHD). However, overall, our results also suggests that the majority of genetic/environmental influences (96%) on chronotype do not overlap with those on the psychopathology factor.

Conclusions: Results from this study highlight existence of significant associations between chronotype and certain psychopathology traits. However, the very small associations do not support the idea that chronotype is a core element of the general "p-factor".