Sleep and Parasympathetic Activity During Rest and Stress in Healthy Adolescents and Adolescents With Bipolar Disorder.

OBJECTIVE: Sleep disruption contributes to the pathophysiology of mental disorders, particularly bipolar illness, but the biobehavioral mechanisms of this relationship are insufficiently understood. This study evaluated sleep duration, timing, and variability as prospective predictors of parasympathetic nervous system activity during rest and social stress in adolescents with bipolar disorder, reflecting sleep-related interference in stress regulatory systems that may confer vulnerability to mood episodes.
METHOD: Participants were adolescents with bipolar disorder (n = 22) and healthy adolescents (n = 27). Sleep duration and timing were measured by actigraphy for 1 week before a laboratory social stress task, during which high-frequency heart rate variability (HF-HRV) was indexed using electrocardiography. Multilevel models were used to evaluate group, sleep characteristics, and their interactions as predictors of initial HF-HRV and change in HF-HRV during rest and stress.
RESULTS: Associations between group and changes in HF-HRV during stress were moderated by sleep duration mean (z = 2.24, p = .025) and variability (z = -2.78, p = .006). There were also main effects of mean sleep duration on initial HF-HRV during rest (z = -5.37, p < .001) and stress (z = -2.69, p = .007). Follow-up analyses indicated that, in bipolar adolescents during stress, shorter and longer sleep durations were associated with lower initial HF-HRV (z = -5.44, p < .001), and greater variability in sleep duration was associated with less change in HF-HRV (z = -2.18, p = .029).
CONCLUSIONS: Sleep durations that are relatively short or long, which are characteristic of mood episodes, are associated with parasympathetic vulnerability to social stress in adolescents with bipolar disorder. Obtaining regular sleep of moderate duration may favorably affect responses to stress in bipolar youth.