Keep a daily sleep diary

Track sleep and wake times daily to reveal patterns and benchmark treatment progress.

Why it works

A sleep diary externalizes subjective sleep perception, which is often distorted in insomnia — people consistently underestimate how much they sleep. It reveals the maintaining patterns that perpetuate insomnia (late bedtimes, excessive time in bed, irregular schedules) and provides the data needed to calculate sleep efficiency for sleep restriction therapy.

How to do it

1. Complete the diary each morning — not at night — covering bedtime, sleep onset estimate, wake times, and morning rise time.
2. Track for at least one week before starting CBT-I to establish your baseline.
3. Review weekly to spot patterns and calculate sleep efficiency (total sleep ÷ time in bed × 100).

Evidence

Sleep diaries are the standard assessment tool in clinical insomnia research and treatment; they are validated against polysomnography for capturing self-reported sleep patterns, and their use is built into all CBT-I protocols. (clinical)

People with insomnia tend to overestimate sleep onset latency and underestimate total sleep; the diary captures subjective experience, which is what CBT-I acts on, even if it differs from objective measures.

Common mistake

Completing the diary in the evening by trying to recall the night, which introduces memory bias; morning recall is more accurate and less likely to prime bedtime anxiety.