Development and initial validation of the Iowa Sleep Disturbances Inventory

The Iowa Sleep Disturbances Inventory (ISDI) is a new measure of self-reported sleep difficulties, which was designed to help facilitate research on the overlap of sleep disturbances and psychopathology. This instrument was developed in two large student samples using principal factor analyses; the psychometric properties of the scales were then examined in three additional samples (students, psychiatric patients, sleep disorder patients). The ISDI consists of 11 specific scales (Nightmares, Initial Insomnia, Fatigue, Fragmented Sleep, Nonrestorative Sleep, Anxiety at Night, Light Sleep, Movement at Night, Sensations at Night, Excessive Sleep, Irregular Schedule) and 1 general scale (Daytime Disturbances). The structure of the ISDI generalizes across both patient and nonpatient samples. In addition, the ISDI scales are internally consistent, show good retest reliability, demonstrate convergent and discriminant validity with widely used measures of sleep disturbances, and display criterion validity in relation to psychiatric patient status and specific symptoms of depression and anxiety.