Abstract

Sleep restriction, a key element of CBT-I involves considerable behavioral changes in patients’
lives, leading to side effects like increased daytime sleepiness. Studies on sleep restriction
rarely report adherence and when assessed it is often limited to the average number of therapy
sessions attended. This study aims to systematically evaluate different measures of adherence
to CBT-I and their relationship with treatment outcome. This is a secondary analysis of data
from a randomized controlled trial investigating CBT-I (Johann et al. 2020). The sample
included 23 patients diagnosed with insomnia according to DSM-5 criteria who underwent eight
weeks of CBT-I. Following adherence measures based on sleep diary data were used: number
of sessions completed, deviations from agreed time in bed; average percentage of patients
deviating from bedtime by 15, 30, or 60 minutes; variability of bedtime and wake-up time;
change in time in bed from pre- to post-assessment. Treatment outcome was assessed using
the Insomnia Severity Index (ISI). Multiple regression models were employed, insomnia
severity was controlled for. Results showed that none of the adherence measures predict
insomnia severity. Baseline insomnia severity, dysfunctional thoughts and attitudes about
sleep, depression, or perfectionism did not predict adherence. The limited variance in the
outcome parameter due to most patients benefiting from treatment and the small sample size
may explain these findings. Additionally, using objective measures like actigraphy could
provide a better understanding of adherence behavior. Lastly, the presence of perfectionism
in insomnia patients may have mitigated adherence problems in this study.