To adequately differentiate between genetic and environmental factors’ impact on sleep, the study amalgamated a large sample of twins to act as participants. Given that twins share the same genotype, or genetics, utilizing twins in the study was crucial to highlight and substantiate the differences between genetically-induced outcomes and environmentally-induced ones. The study first assessed each participant’s personality type and then measured their sleep quality by a uniform metric of initiation ease, interruptions (if any), and perceived restoration. The findings were then compared to each participant’s respective measurement of various personality traits, including neuroticism, positive affectivity, planfulness, achievement-striving, stress-reaction, well-being, hostility, and aggressiveness.
Ultimately, the study found that all tested personality traits except achievement-striving were correlated with one’s subjective sleep quality, with poor sleep contributing to a weakened manifestation of said traits. Notably, participants’ stress reactions and well-being had the most notable correlation with sleep quality. The study also found that the correlation between sleeping patterns and personality traits is driven largely by genetic factors rather than environmental ones, highlighting that twins generally shared similar sleeping patterns and personality traits regardless of their respective life predicaments.