Limitations
sleep disorders, psychiatric, insomnia
ADVERSE EVENTS
Exclusion criteria of the study means that findings may not generalize to individuals with comorbid insomnia and severe physiologically based sleep disorders or those with severe psychiatric or health conditions. The sample was mostly White, in a relationship, and working full-time, further limiting findings to more diverse samples. Missing data on sleep wearable devices, especially on the EEG Dreem headband, may have impacted the quality of sleep reports that participants received. This study occurred throughout the COVID-19 pandemic, and although participants reported relatively small impact of the pandemic on their participation and overall well-being, findings may not be generalized to different societal contexts and timeframes. This manuscript did not explore physiological mechanisms of sleep–wake state discrepancy (e.g. using EEG derived from Dreem), which needs to be explored in future research. We did not use a questionnaire to systematically assess itemized adverse events, but all participants were proactively asked about adverse events at each contact. Finally, this study did not explore individual differences in responses to the intervention; it is possible that some individuals with insomnia may benefit, whilst others do not benefit from receiving sleep feedback, and factors predicting these responses require future research.