Insomnia is a key risk factor for persistent anxiety and depressive symptoms: A 12-month longitudinal cohort study during the COVID-19 pandemic.

Background: Insomnia is a risk factor for affective disorders. This study examined whether individuals with insomnia symptoms early in the pandemic, either pre-existing or new-onset, were more vulnerable to anxiety and depressive symptoms over time than those who maintained normal sleep. Additionally, sleep-related factors such as pre-sleep arousal were assessed for their influence on clinically significant anxiety and depression risk.

Methods: Using a global online survey with 3-, 6-, and 12-month follow-ups between April 2020 and May 2021, data from 2069 participants (M = 46.16 ± 13.42 years; 75.3 % female) with pre-existing, new-onset, or no insomnia symptoms was examined using mixed-effects and logistic regression models.

Results: New-onset and pre-existing insomnia predicted persistent anxiety and depressive symptoms longitudinally (p's < 0.001), over other known risk factors, including age, sex, and previous psychiatric diagnoses. Anxiety and depressive symptoms in both insomnia groups remained above clinically significant thresholds at most time points, whereas normal sleepers remained subclinical. Pre-sleep arousal was found to increase the risk of clinically significant anxiety (OR = 1.05) and depressive symptoms (OR = 1.09) at 12-months. Sleep effort contributed to anxiety (OR = 1.06), whereas dysfunctional sleep-related beliefs and attitudes predicted clinically significant depression (OR = 1.22).

Limitations: Insomnia group categorization was based on self-report at baseline supported by a validated measure. High participant attrition was observed at 3-months (53 %; n = 971), but retention remained steady till 12-months (63 %, n = 779).

Conclusions: Insomnia is a modifiable risk factor for persistent anxiety and depressive symptoms that needs to be addressed in mental healthcare. Additionally, pre-sleep arousal may be an important transdiagnostic process linking insomnia with affective disorders.