Being a 'night owl' may raise risks of mood swings and bipolar traits, study finds

Around one in three adults in the UK and Europe consider themselves 'night owls'—people who naturally stay up late and struggle with early mornings. New research now links this evening chronotype to a higher risk of mood instability and subthreshold bipolar traits. The findings come from a study of over 2,000 adults, where sleep patterns and emotional regulation were closely examined. The study surveyed 2,031 adults, dividing them into three groups: 22.8% identified as evening types, 22.2% as morning types, and 55.0% as neutral. Those with an evening chronotype showed far greater emotional dysregulation than morning or neutral types. They also scored higher on measures of depressive, anxious, irritable, and cyclothymic temperaments—traits often linked to bipolar vulnerability.

Higher 'eveningness' scores strongly correlated with poorer emotional control and more pronounced affective temperaments. Participants with this sleep pattern also recorded elevated scores on the MDQ and HCL-32-R2 scales, both used to detect subthreshold bipolar disorder. Tobacco use, alongside evening chronotype, emerged as the only significant predictors of these bipolar-like features in detailed statistical analyses. Good sleep quality, however, appeared to act as a protective factor. Those reporting excellent rest showed lower risks of subthreshold bipolar symptoms, regardless of chronotype. Yet, despite these findings, no specific guidelines or preventive measures have been proposed by European psychiatry experts for assessing or supporting at-risk individuals.

The research highlights a clear connection between evening chronotype and emotional instability, particularly traits associated with bipolar vulnerability. While quality sleep may reduce some risks, no formal recommendations currently exist for managing these risks in clinical settings. The findings suggest a need for further investigation into tailored support for late-night individuals.