Rest-activity rhythm robustness and prospective mood symptoms in adolescence: Moderating effects of chronotype, sleep timing, and reward sensitivity

Adolescence is a period of heightened bipolar spectrum disorder (BSD) risk involving changes in reward and circadian systems. Circadian disruptions can destabilize mood, and the impact may be more pronounced in individuals with trait vulnerabilities. We tested whether greater reward sensitivity or eveningness influenced the predictive association between rest-activity rhythm (RAR) disruption and dimensional mood symptoms relevant to BSD.

Adolescents (N = 199) in a prospective BSD-risk study completed baseline measures of reward sensitivity, morningness-eveningness, mood symptoms, and one week of actigraphy to generate Circadian Function Index (CFI), a composite measure of RAR robustness. Mood measures were readministered six months later. Regression models tested interactions between reward sensitivity, morningness-eveningness, and sleep midpoint and CFI to predict hypo-/manic or depressive symptom severity at follow-up.

CFI was not independently associated with mood symptoms. Morningness-eveningness (b = 0.59, p < .001) and sleep midpoint (b = -2.77, p = .013) significantly moderated the association between CFI and hypo-/manic symptoms. Sleep midpoint (b = -5.40, p = .023) and reward sensitivity (b = -1.32, p = .033) significantly moderated the association between CFI and depressive symptoms.

The impact of CFI on mood symptoms depended upon vulnerabilities. Lower CFI predicted greater hypo-/manic symptoms among adolescents with greater eveningness and later sleep midpoint. Lower CFI predicted greater depressive symptoms among those with later sleep midpoint. Contrary to hypotheses, higher CFI predicted greater depressive symptoms for adolescents with reward hyposensitivity. These results highlight potential targets for future identification studies relevant to BSD.