# Chronotype and psychopathology: insights from a genetically informative design

## TL;DR

This study explores how a person's natural sleep pattern (chronotype) relates to mental health issues and finds small but significant links, though it is not a core mental health risk factor.

## Contribution

The study uses a genetically informative design to clarify whether chronotype is a transdiagnostic risk factor for psychopathology or part of a broader mental health construct.

## Key findings

- Chronotype shows small but significant associations with psychopathology traits like depression and anxiety.
- Most genetic and environmental influences on chronotype (96%) are distinct from those affecting psychopathology.
- Polygenic scores for chronotype predict only a small proportion of variance in some psychopathology measures.

## Abstract

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 conceptualized as a part of the global construct of psychopathology (p-factor) by studying the genetic and environmental overlap between these variables. We utilize 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.

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.

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 attention deficit hyperactivity disorder). However, overall, our results also suggest that the majority of genetic/environmental influences (96 per cent) on chronotype do not overlap with those on the psychopathology factor.

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.”

Statement of Significance Chronotype (and primarily late chronotype) has been linked to a wide variety of psychiatric conditions. This study deepens understanding of the association between chronotype and psychopathology, by comprehensively exploring this association using a genetically informative design. Our results reveal small but largely significant associations between chronotype and mental health variables and provide new insights into the etiology of these associations. This report considers whether late chronotype, which many consider to be a transdiagnostic risk factor for psychopathology, could be integrated in the global factor of psychopathology. Overall, our results suggest that while there are significant associations between chronotype and psychopathology traits—these associations are small and chronotype is largely influenced by genetic/environmental influences distinct from those on the psychopathology factor (more than 96 per cent) and should not be considered as a core feature of this construct.

Graphical Abstract