People prone to frequent worry and anxiety often complain of a lack of sleep. However, a new study published in the journal Personality and Individual Differences showed that a trait such as neuroticism (a tendency to experience negative emotions) is linked more to how much sleep a person says they get than to how much sleep a special wristband actually records.
The study involved 134 undergraduate students (mean age 19, 95 women) without diagnosed sleep disorders. Over five nights, including two weekend nights, they wore an actigraph on the wrist, a device that estimates sleep from body movements. In addition, participants completed questionnaires about their personality, sleep, and symptoms of depression and anxiety.
Sleep over the past month was assessed in two ways. In the first, participants themselves indicated how many hours of actual sleep they usually get. In the second, researchers calculated sleep duration from usual bedtime, wake time and sleep-onset time.
The results showed that the higher the level of neuroticism, the less sleep participants reported in both self-reports. However, no such link was found with the actigraph data. The difference was small: each point on the five-point neuroticism scale corresponded to about 15-20 minutes less reported sleep. The link persisted even after accounting for actigraph data, demographic characteristics, body mass index, symptoms of depression and anxiety, sleep regularity and other personality traits.
Average sleep estimates clearly showed how the measurement methods differ. When asked directly, participants reported 6.74 hours of sleep, the actigraph estimated sleep at 6.70 hours, and the calculated self-report gave a higher result, 7.40 hours. Compared with the actigraph, people with higher neuroticism tend to understate their sleep when asked directly and to overstate it less with the calculated method.
Symptoms of depression and anxiety were closely linked to neuroticism, but on their own did not affect how much participants slept or reported sleeping. Accounting for them did not weaken the link found. The authors suggest the explanation may lie in a stable personality trait rather than a temporary ailment.
The researchers write that the results "are consistent with the possibility that neuroticism is more strongly linked to how a person perceives, remembers and reports the duration of their sleep than to the duration recorded by an actigraph." They suggested that people high in neuroticism may recall or interpret their sleep more negatively, and that anxiety before sleep may create a sense that falling asleep takes longer. However, these explanations remain hypotheses, since memory errors and reporting bias were not measured directly.
The authors also noted other possible causes. People high in neuroticism may lie in bed without sleeping for longer, and an actigraph sometimes takes such a state for sleep. In addition, both neuroticism and habitual sleep were assessed by self-report, so part of the link may be explained by shared features of self-reporting.
The study has limitations. The questionnaires asked about sleep over the past month, while the actigraph recorded only five nights, which may not be enough for a reliable estimate of habitual sleep; this also complicates direct comparison. Participants may have changed their sleep knowing they were being observed, and the sample consisted of students at a single private university, most of them women.
It is important to emphasize that the study found a statistical association, not a causal one. This means neuroticism may be linked to how a person assesses their sleep, but it does not prove that it causes changes in sleep perception.