The prevalence of obesity in the United States has increased dramatically over the last several decades. The National Center for Health Statistics found in 2003 to 2004 that 17.4% of children and adolescents were overweight and 32.9% of adults were obese [1
]. Additionally, among adolescents 11 to 16 years old over one-quarter (26.6%) were obese [2
]. Adolescence is an especially vulnerable period for considering overweight and obesity issues, as during adolescence multiple social, cognitive, and emotional transitions occur as a normative part of development [3
]. Psychopathology such as eating disorders, substance abuse, and depression may materialize during this period [3
]. Additionally, sleep patterns shift and sleep duration is lessened [4
], which can have an impact on both emotions and obesity. Therefore, the focus of this report is to examine body mass index and sleep chronotype and their association with depressive symptoms and anxiety in female adolescents.
Depression and anxiety are common in adolescents and young adults, with anxiety often preceding depression [5
]. According to the Department of Health and Human Services, 10% to 15% of children and adolescents experience depressive symptoms [6
]. Many studies have examined whether overweight adolescents are more likely to be depressed than their normal weight peers. Pine et al [7
] longitudinally examined the relationship between psychopathology and obesity in both male and female adolescents. Depression and obesity were positively associated in females and the entire sample, but not in males [7
]. Similar results were observed in a large cross-sectional, population-based sample of adolescents. Obese girls were more likely to report more serious emotional problems, hopelessness, and a suicide attempt in the last year, when compared to their normal weight peers [8
]. Likewise, anxiety disorders were associated with higher weight in both adolescent and adult females [9
]. Female adults with a lifetime diagnosis of anxiety were 1.4 times more likely to be obese than those without a diagnosis [10
]. In contrast, community-based, cross-sectional studies [11
] indicate no difference in the incidence of depression between overweight and normal-weight children and adolescents. Discrepancies in these results are seemingly because of differing methodologies (longitudinal vs. cross-sectional clinic vs. community vs. population). As obesity in adolescence continues to rise, it is paramount to study its association with adolescent psychopathology given the high prevalence of both obesity and affective problems in girls.
Overweight children and obese adults report less sleep than those of normal weight [13
]; however, what remains uncertain is whether sleep preference is associated with increased body weight. Sleep preference refers to the time when individuals prefer to sleep and to be alert and working. This preference has been referred to as morningness (larks) or eveningness (owls) [17
]. Morning types (M) awaken and retire earlier and show less erratic sleep duration than evening types (E). E-types prefer to sleep later and in the morning and find it arduous to rise. One’s preference for sleep (chronotype) is a measure reflecting chronobiology or biological rhythms, and to some extent is based on genetics [19
]. Chronotype may change across the life span. For example, prepubertal children (7–9 years old) are more likely to be M-types, waking independently and at the same approximate time each morning [20
]. Alternatively, during puberty and adolescence, sleep preference shifts to eveningness, as this is a period of increased academic demands and social opportunities. Late bedtime during adolescence is common, as chronotype shifts during this period [4
] toward a preference for staying up late [23
]. Teens who spend more late night hours awake have increased tiredness and are more likely to report daytime sleepiness. These sleep patterns may contribute to other unhealthy choices such as: more infrequent meals, snacking, and a decreased tendency to participate in organized sports [23
]. One could speculate that with erratic eating habits and a lack of exercise, E-types would be more likely to have greater body weight when compared with M-types. Although research is limited in this area, one cross-sectional study observed a trend between evening sleep preference and higher body mass index (BMI) in adolescents [21
]. In addition, E-type adolescents are also more likely to have emotional problems such as depression and anxiety [24
Although evening sleep preference may be advantageous for enhanced social experiences (activities with peers) from the adolescent’s perspective, an E preference may also increase opportunities for risky behaviors and the likelihood of emotional problems [26
]. For example, in Chinese adolescents suicidality was more prevalent in those with evening preference (34.4%) than intermediate or morning preferences (20.5% and 18.5%) [24
]. Additionally, E-types presented with more emotional problems such as depression and anxiety, than their M-type peers [27
]. Obesity and psychopathology that develop during adolescence may initiate health and emotional problems that persist into adulthood therefore, examination of these associations in adolescents is warranted.
The first aim of this study was to examine the differences in depressive symptoms and anxiety, by BMI group (i.e., normal weight: <85th percentile vs. overweight: ≥85th percentile) and sleep chronotype (morning vs. evening preference). The second aim was to examine the interaction between sleep chronotype and BMI group on depressive symptoms and anxiety. To our knowledge, this is the first study to examine the associations between sleep preference, BMI, depression, and anxiety in pubertal age females. Findings may assist in identifying the overlapping risk of obesity, sleep chronotype, and depression and anxiety in pubertal age females.