2.2.6 Insomnia Severity Index (ISI)
The ISI is a valid and reliable tool to assess perceived insomnia
severity. It was developed by Bastien et al.17. The
validity and reliability studies of the scale in the Turkish population
were conducted by Boysan et al.18. It evaluates the
severity of sleep onset, sleep maintenance, early morning awakening
problems, satisfaction with current sleep pattern, interference with
daily functioning, noticeability of impairment, and level of distress
caused by the sleep problem. Each item is scored on a 5-point
Likert-type scale and higher scores indicate greater insomnia severity.