Psychological symptoms and insulin sensitivity in adolescents.

Low insulin sensitivity is a major physiological precursor to type 2 diabetes and an important risk factor for the development of cardiovascular disease [1]. One of the primary pathways by which decreased insulin sensitivity develops is through excessive gain of body fat. Overweight youth have decreased insulin sensitivity compared to their non-overweight counterparts, placing them at heightened risk for negative health consequences including type 2 diabetes [2]. However, evidence from adult studies suggests that psychological factors may also affect insulin sensitivity [3–11]. In overweight and non-overweight adults, sub-clinical and clinical threshold depressive symptoms are correlates of, and potential risk factors for, the development of decreased insulin sensitivity [3, 6–10], type 2 diabetes [5, 12, 13], and other aspects of the metabolic syndrome [4, 11]. The degree of psychosocial stress and anxiety symptoms in a large community sample of women also has been shown to be significantly related to measures of insulin sensitivity, even after accounting for body mass index [4]. From a psychophysiological theoretical perspective, depression or anxiety are believed to impact insulin sensitivity through physiological mechanisms such as altered insulin signaling in the brain, pro-inflammatory activation, and/or distress-induced upregulation of counterregulatory hormone systems [14, 15]. In addition, from a behavioral psychology perspective, depression and stress may affect insulin sensitivity, in theory, through their impact on lifestyle factors such as physical inactivity. Given the possible role that adult studies suggest for depression and anxiety in the development of decreased insulin sensitivity, understanding how these factors are linked to glucose homeostasis during adolescence may be important for identifying early risks for potentially adverse health outcomes. Parents’ perceptions of their children’s negative emotionality have been found to be associated with children’s fasting insulin, particularly among boys, in a large study of Finnish youth ages 6 to 18 years [16]. To our knowledge, however, no studies to date have examined the links between depressive or anxiety symptoms and fasting insulin or measures of insulin sensitivity in youth. Adolescence represents an important developmental stage for understanding the links between psychological symptoms and insulin sensitivity. During adolescence, normative endocrine changes associated with puberty produce decreased insulin sensitivity relative to childhood. Moreover, adolescence marks a peak time for the onset of depressive symptoms, particularly among girls. Thus, these marked psychological and biological shifts render adolescence an important developmental stage for understanding how symptoms of depression are associated with insulin sensitivity. We, therefore, investigated whether symptoms of depression and anxiety were associated with insulin sensitivity among adolescents. Based upon prior data, we hypothesized that symptoms of depression and anxiety would be associated with higher fasting insulin and decreased insulin sensitivity. Since previous literature has indicated that sex may act as a moderator of the association between psychological symptoms and insulin sensitivity [9, 16], we expected that sex might interact with depression or anxiety and their association with insulin measures, such that the effects would be stronger for girls than for boys.