People with sleep-onset problems often experience neuroticism. To what extent the one problem leads to the other is unknown. We used self-reported data from a Swedish longitudinal project to examine developmental links between neuroticism and sleep-onset problems. A sample of 212 people, followed from birth to midlife, was part of a cohort study spanning 37 years. Adolescent neuroticism was measured at age 16 with the High School Personality Questionnaire (HSPQ, Form A) and in midlife at age 37 with the Eysenck Personality Questionnaire (EPQ). Sleep-onset problems were measured at ages 15 to 17, 25, and 37 with items developed for the Solna Project. Adolescent neuroticism failed to predict sleep-onset problems. Instead, sleep-onset problems in adolescence and young adulthood predicted midlife neuroticism. We found that sleep-onset problems during adolescence were a direct risk for midlife neuroticism, as well as, an indirect risk through continuance of sleep-onset problems into adulthood. This study provides longitudinal support for adolescent sleep-onset problems as a potent risk factor for heightened neuroticism in midlife.
Some people with sleep-onset problems experience symptoms resembling neuroticism. Neuroticism, also known as negative affectivity or trait anxiety (Watson & Clark, 1984), is a genetically and environmentally influenced personality trait (McCrae et al., 2001 and Vernon et al., 1997). Traits predispose people to perceive and experience their environment in characteristic ways (Buss & Plomin, 1984). As such, neuroticism is a tendency toward negative emotions, cognitions, and behaviours (Jang et al., 1998 and Watson et al., 1994). Likewise, sleep-onset problems have emotional (e.g., Dahl & Lewin, 2002), cognitive (e.g., Roth, 2007), and behavioural components (e.g., Perlis, Giles, Mendelson, Bootzin, & Wyatt, 1997). Similarities suggest that one problem may be important for the other.
Theoretically, processes involved in the development of insomnia, especially sleep-onset problems, are hierarchical. These are predisposing conditions, precipitating circumstances, and perpetuating factors (e.g., Drake & Roth, 2006). Processes may include biological (e.g., Espie, 2002) and genetic (Watson & Goldberg, 2006) predisposition; stressful life-event precipitation (Vahtera et al., 2007); and physiological (e.g., Perlis et al., 1997), cognitive (e.g., Harvey, 2002), and behavioural (e.g., Perlis et al., 1997) perpetuation. Potentially the association occurs on all levels.
Perhaps neuroticism predisposes some people to react toward life-stressors with negative emotions, cognitions, and behaviours incompatible with falling asleep. Predisposition alone is likely insufficient for developing sleep-onset problems (e.g., Drake & Roth, 2006). Instead, life-stressors may aggravate neuroticism, thus contributing to sleep-onset problems. On the other hand sleep-onset problems may heighten neuroticism. Typical ways people with sleep-onset problems feel, think, and react is like that for neuroticism (e.g., Dorsey and Bootzin, 1997, Freedman and Sattler, 1982, Shealy et al., 1980 and Vahtera et al., 2007). Unknown is the nature of the association.
Indeed, sleep-onset problems are associated with neuroticism. College students with sleep-onset problems reported higher neuroticism compared to controls (Shealy et al., 1980). In a laboratory, university students subjectively experiencing sleep-onset problems, reported more neuroticism than students with objective sleep-onset problems (Dorsey & Bootzin, 1997). The direction of the relation is unclear.
The few studies about neuroticism and sleep-onset are cross-sectional or retrospective. Which problem precedes or precipitates the other cannot be determined with these methods. Retrospective reports have the added disadvantage of memory distortion. Neuroticism may result in sleep-onset problems, or sleep-onset problems may spur emotional instability. Only longitudinally can the long-term relation be determined.
Our aim is to examine developmental associations between these two problems. The longitudinal design enables us to examine the long-term relation between neuroticism and sleep-onset problems. Specifically, is neuroticism predictive of sleep-onset problems or vice versa? To our knowledge, this is the first study to examine the long-term connection between neuroticism and sleep-onset problems.
