According to research by an Iowa State University psychologist, how well you sleep may depend as much on your personality as it does on your habits.
Zlatan Krizan, professor of psychology, has spent more than a decade studying how personality traits affect both the perception and quality of sleep. His work suggests that people who are more emotionally unstable and less conscientious not only feel like they sleep poorly – they actually do.
“Personality differences explain a lot of why some people are more anxious or depressed than others,” Krizan said. “Those same emotional differences also show up in sleep behavior.”
A natural link between personality and sleep
Recognizing the central role of emotional regulation in both sleep quality and personality traits, Krizan identified a natural connection between the two domains.
Krizan’s 2019 study titled, “Personality and Sleep: Neuroticism and Conscientiousness Predict Behaviourally Recorded Sleep Years Later,” published in the European Journal of Personality, showed that individuals high in neuroticism and low in conscientiousness not only perceived poorer sleep but also exhibited fragmented sleep.
The research utilized self-reported sleep diaries and actigraphy – a method that uses wearable devices to track sleep patterns through movement-based monitoring.
This dual method approach allowed researchers to assess whether personality traits such as neuroticism and conscientiousness correlated with actual disruptions in sleep beyond mere self-reports.
“We wanted to see whether personality was just influencing people’s impressions of how they sleep, or if it also affected how they actually sleep,” Krizan said. “And it turns out the connection is very real.”
When sleep feels worse than it is: Paradoxical insomnia
Krizan’s research also explores the idea of “paradoxical insomnia,” or “sleep state misperception,” where people believe they are sleeping far worse than they are.
This misperception, he found, is more common among individuals with high emotional instability, as distressed individuals tend to overestimate the extent of their sleep disruption. This further supports the idea that personality traits can shape sleep behavior and how that behavior is interpreted.
“Some people might wake up once or twice and think they’ve been awake all night,” Krizan said. “That disconnect between perception and reality often comes down to how sensitive someone is to emotional or physical changes.”
Genetic and developmental links: Twins
Collaborating with colleagues at the University of Minnesota – particularly in their twin studies – Krizan examined genetic foundations of the sleep-personality link and whether certain personality traits and sleep disturbances share the same genetic roots.
In a 2023 article published in the Journal of Sleep Research, Krizan and his co-authors explain connections among middle-aged twins to identify whether inherited traits could underlie chronic sleep problems.
Beyond genetic influences, Krizan examines how sleep and personality shape each other over time. Poor sleep in childhood may affect emotional development and long-term personality traits – and whether early personality characteristics can set children on a path toward sleep difficulties.
Sleep, law, and public health
In addition to foundational research, Krizan explores the intersection of sleep and law. His work connects how sleep deprivation affects behavior in high-stakes environments such as police interrogations and crisis situations.
While mentoring graduate and undergraduate students at Iowa State, Krizan also partners with researchers from other institutions. His work utilizes publicly available data from sources like the National Institutes of Health, allowing for representative sample sizes.
“There’s growing recognition that sleep isn’t just a health issue – it’s a psychological one, too,”
Krizan said. “Understanding the personality side of it can help us find better ways to promote
well-being across the lifespan.”