Adverse childhood experiences, insomnia, and depressive symptoms in later life: moderation effect of loneliness but not hair cortisol

Objectives Adverse childhood experiences (ACEs) are established risk factors for developing depression in adulthood, although the mechanisms of this association are yet to be fully elucidated. In this study, we tested whether insomnia (i.e., difficulties in sleep onset and maintenance) can mediate the association between ACEs and adult depressive symptoms, and whether loneliness and hair cortisol, reflecting hypothalamic-pituitary-adrenal axis activity, can act as moderators. Methods We analyzed data of 1593 participants (64.7% female) aged 65.25 ± 8.15 from the English Longitudinal Study of Ageing (ELSA) across three waves of data collection. ACEs were retrospectively assessed in 2008–2009 (wave 4), insomnia symptoms, loneliness, and hair cortisol in 2012–2013 (wave 6), while depressive symptoms were assessed in 2014–2015 (wave 7). Results After accounting for health-related confounders and baseline values, conditional process analysis showed that insomnia symptoms exerted a mediating role between ACEs (ACEs total, parental bonding, and household dysfunction) and depressive symptoms, with a stronger effect in lonely older adults. Hair cortisol did not moderate the association between ACEs and insomnia symptoms. Conclusion Results are consistent with the view of insomnia as a mechanism linking ACEs to depressive symptoms later in life. Elderly experience of loneliness may further increase the mediatory role of insomnia between ACEs and depression.