TABLE 3.

Intraindividual standard deviation (ISD) based on 1 week of sleep diary recording, as a measure of day-to-day variation in sleep in the participants with delayed sleep–wake phase disorder (DSWPD) and controls.

	Controls (n = 21)	DSWPD (n = 40)	Effect size	T-test
	Mean ± SD	Mean ± SD	Cohen’s d	p
Sleep diary
Bedtime (min)	71 ± 36	85 ± 40	0.37	0.179
Rise time (min)	64 ± 37	84 ± 47	0.47	0.091
Sleep onset latency (min)	13 ± 18	31 ± 32	0.69	0.005
Total sleep time (min)	14 ± 34	107 ± 43	0.85	0.004
Sleep efficiency (%)	4.4 ± 3.3	7.9 ± 6.3	0.69	0.006

The table shows mean ± standard deviation (SD), Cohen’s d as a measure of effect size and results from independent samples t-tests.