Type D personality is associated with sleep problems in adolescents. Results from a population-based cohort study of Swedish adolescents
Introduction
Type D personality, or the distressed personality, refers to the joint tendency to experience negative emotions and to inhibit self-expression in social interaction [1]. It is characterised by two global personality traits: negative affectivity and social inhibition [2]. This personality has been associated with increased morbidity and mortality in patients with cardiovascular disease [3], [4], [5], [6], [7]. Type D personality is also associated with several emotional and social difficulties such as depression, anxiety, low level of subjective well-being, lack of social support and low quality of life which have a negative impact on mental and physical health [8], [9], [10], [11], [12]. Furthermore, individuals with this personality type may be more likely to engage in maladaptive health behaviours, such as a sedentary life style [13], [14].
A large body of research shows the important role of sleep in somatic, cognitive and psychological processes [15]. Sleep is an active process in the brain that is necessary for restorative functions, particularly during development [16], [17]. Moreover, sleep serves an important role in body homeostasis such as metabolic, immune, thermoregulatory and respiratory functions [15].
The amount of sleep hours received is an important indicator of health and well-being among adolescents. Adolescence is a vulnerable period, during which many physiological, cognitive and psychological processes mature [15], [17]. In fact, poor sleep habits later on in life are often established during adolescence [18]. Most research has proposed that adolescents require at least 6–8 h of sleep each night [19]. A population-based study on adolescents showed that the prevalence of restricted sleep, i.e. < 6 h, was 20% [20]. Associations have been found between adequate sleep among adolescents and life appreciation, anxiety, depressive symptoms, stress management and health behaviour [21], [22], [23], [24].
Studies investigating the associations between personality dimensions and sleep are sparse. Bertelson and Monroe showed a relationship between neuroticism and sleep disturbance in adolescents, and also demonstrated a similarity of personality dynamics of adolescents with sleep problems [25]. Vincent et al. found associations between short sleep and neuroticism, suggesting an association between personality and sleep length [26].
Recently, De Fruyt and Denollet identified Type D personality as a significant predictor of sleeping problems in adults [27]. Type D personality with its subcomponents of negative affectivity and social inhibition may be a risk factor for poor sleep among adolescents as well. The aim of the present study was, therefore, to investigate the associations between Type D personality and sleep problems among adolescents. We hypothesised that Type D personality is associated with sleep problems among adolescents.
Section snippets
Methods
The study was part of the Survey of Adolescent Life in Västmanland 2008 (SALVe 2008), a survey distributed biannually by the County Council of Västmanland in order to monitor the psychosocial health of the adolescent population of the county. Västmanland is situated about 100 km west of Stockholm, and is a middle sized representative region of Sweden due to its mix of rural and urbanised areas. All the students in the county in the 9th grade of elementary school (15–16 years old) and the 2nd year
Results
Type D personality was more common among the girls in this study (Table 1). As there are several factors already well known to contribute to sleep problems among adolescents such as alcohol use, exercise habits, smoking, excessive computer use and family socioeconomic status (SES), these factors were included as control variables in the statistical analyses. Boys reported a higher alcohol consumption (boys M = 4.94; SD = 4.24; girls M = 4.35; SD = 3.50; Z = − 3.78; p ≤ .001), a higher family SES (boys M =
Discussion
The main finding was that Type D personality was associated with increased sleep problems among adolescents. Adolescents with Type D personality had a four times increased risk of having sleep disturbances. Moreover, Type D personality was associated with sleeping fewer hours. Statistical correlations between sleep problems and main and control variables were weak, although they all contributed to the results. When the two subscales of Type D personality were analysed separately, the NA
Conflict of interest
The authors have no conflict of interest.
Acknowledgments
The authors would like to acknowledge the help of Professor Jerzy Leppert for his critical revision of the manuscript. Grants from the following funds and organisations are acknowledged: The Uppsala and Örebro Regional Research Council, Fredrik and Ingrid Thurings Foundation, the County Council of Västmanland, König-Söderströmska Foundation, The Swedish Psychiatric Foundation, and The Swedish Council for Working Life and Social Research (FAS). The sponsors of the study had no role in the study
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