Assessing insomnia severity in depression: comparison of depression rating scales and sleep diaries.

Depression and sleep researchers typically assess insomnia severity differently. Whereas depression researchers usually assess insomnia with items on depression symptom inventories, sleep researchers usually assess the subjective experience of insomnia with sleep diaries. The present manuscript utilizes baseline data from 397 participants in a large multi-site chronic depression study to assess agreement between these two methodologies. The results indicate that the early, middle, and late insomnia items of the Hamilton Rating Scale for Depression (HRSD(24)) and the Inventory of Depression Symptoms - Self Report (IDS-SR(30)) are highly correlated with the weekly mean values of time to sleep onset, time awake after sleep onset, and time awake prior to the planned wake-up obtained from prospective sleep diaries. Results also reveal significant correspondence between the weekly-mean of daily sleep efficiency, an accepted measure of sleep continuity (the ratio between reported time asleep and time in bed), and the insomnia scale scores of the HRSD(24) and the IDS-SR(30) (the mean score on the three insomnia items of each depression measure). Unit increments in HRSD(24) scores for early, middle and late insomnia were associated with significant increases in unwanted minutes awake for corresponding periods on sleep diaries. Similar relationships were found for early insomnia on the IDS-SR(30) but not for middle and late insomnia. Overall, with few exceptions, findings revealed substantial agreement between the HRSD(24), IDS-SR(30) and prospective sleep diary data. The study supports the validity of the sleep items and sleep subscales of the HRSD(24) and the IDS-SR(30) as global measures of insomnia severity in depression. Conventional sleep assessment procedures can complement depression scales by providing additional information about specific aspects of sleep in depression.