Objectives: Validation of self-report assessment of habitual sleep duration and onset time in young people with mental ill-health.

Design: Validation sample.

Setting: Specialized early intervention centers for young people in Sydney, Australia.

Participants: One hundred and forty-six young people with mental ill-health.

Intervention: N/A.

Measurements: Self-reported habitual sleep duration and onset time were compared against at least 7 days of actigraphy monitoring. Average bias in and calibration of subjective measures were assessed, along with correlation of subjective and objective measures. Differences by age, sex, mental-disorder type, and reported insomnia were also explored.

Results: On average, subjective estimates of sleep were unbiased. Overall, each additional hour of objective habitual sleep duration predicted 41 minutes more subjective habitual sleep duration, and each hour later objective habitual sleep onset occurred predicted a 43-minute later subjective habitual sleep onset. There were subgroup differences: subjective habitual sleep duration in self-reported insomnia was shorter than objective duration by 30 minutes (SD = 119), on average. Calibration of habitual sleep duration was worse for those with mood disorders than with other primary diagnoses (t = -2.39, P = .018). Correlation between subjective and objective measures was strong for sleep onset time (Á = .667, P < .001) and moderate for sleep duration (r = .332, P < .001). For the mood disorder group, subjective and objective sleep durations were uncorrelated.

Conclusions: Self-reports seem valid for large-scale studies of habitual sleep duration and onset in help-seeking young people, but assessment of habitual sleep duration requires objective measures where individual accuracy is important.