New research published in the European Journal of Personality has found that some personality traits are connected to how long and how well people sleep.

“Sleep is very dynamic and biologically regulated, yet is also a personal characteristics,” said study author Zlatan Krizan, a professor of psychology at Iowa State University.

“Uncovering which personality features predict the nature and rhythm of our sleep is important from a theoretical perspective as well as clinical. Plus I have to admit that my life-long insomnia motivated me find what sleep may show about who we are.”

The researchers analyzed data from 382 individuals who participated in the Midlife Development in the U.S. Study. The study included two initial assessments of basic personality traits. A few years later, the participants wore actigraph sleep monitoring devices and provided daily evaluations of their sleep quality for one week.

The findings indicated that two of the Big Five personality traits were related to sleep quality. The researchers found that more neurotic and less conscientious individuals tended to have more disturbances during their sleep. More neurotic individuals also tended to have greater variability in how long they slept.

“How a person sleeps is partially reflective of their personality constitution. For example, individuals more prone to negative emotions and difficulties with self-control had more variable sleep from one night to the next, which may point to important everyday routines (or the lack thereof) that could be producing such ups and downs,” Krizan told PsyPost.

“One cannot change one’s personality just like that, but can identify ways in which to get out of one’s own way!”

The study — like all research — includes some limitations. The study relied on cross-sectional data, making it difficult to determine the direction of causality. In other words, it is unclear whether personality impacts sleep or whether sleep impacts personality.

“Exactly how personality intersects with sleep is still relatively unknown,” Krizan said. “Most research is based on questionnaires, so more studies like this one where more objective methods are used, as well as where real-life sleep is sampled are necessary to further our understanding.”

“Moreover, personality is likely to matter for the makeup of the sleep episode themselves, so leveraging modern sleep-monitoring technology will be critical.”

The study, “Personality and Sleep: Neuroticism and Conscientiousness Predict Behaviourally Recorded Sleep Years Later“, was authored by Zlatan Kri┼żan and Garrett Hisler.