Further Validation of the Iowa Sleep Disturbances Inventory
Erin Koffel
July 17, 2011 DOI: 10.17077/4r59-1v3w (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Psychometric validation study |
|---|---|
| Sample size | 419 |
| Population | 219 college students and 200 psychiatric patients |
| Measures | Iowa Sleep Disturbances Inventory (ISDI), clinician rating version of the ISDI |
| Citations | 3 |
| Key points | The expanded ISDI showed strong convergent and discriminant validity with clinician interview ratings (mean convergent correlations .68 in students, .70 in patients; convergent exceeded discriminant in 99.8% of 624 comparisons). The authors report that Sleep Paralysis, Sleep Hallucinations, and Nightmares define a higher-order Unusual Sleep Experiences factor distinct from Insomnia and Lassitude, with Lassitude specific to dysphoria and Unusual Sleep Experiences specific to PTSD and dissociation. |
Abstract
This study examined the reliability and validity of an expanded version of the Iowa Sleep Disturbances Inventory (ISDI; Koffel & Watson, 2010) in 2 samples (219 college students and 200 psychiatric patients). The expanded ISDI includes the scales of Sleep Paralysis and Sleep Hallucinations. These scales, along with the Nightmares scale, help define a higher order factor entitled Unusual Sleep Experiences. This factor was distinct from the factors of Insomnia and Lassitude that were reported previously. The expanded ISDI showed strong evidence of convergent and discriminant validity with the corresponding interview ratings on a clinician rating version of the ISDI. Mean convergent correlations were .68 in students and .70 in patients. Convergent correlations were significantly higher than discriminant correlations in 99.8% of the 624 comparisons. This study also reports the associations of higher order sleep factors with questionnaire and interview measures of pathological symptoms (e.g., depression, anxiety, dissociation, and schizotypy). The Lassitude factor was specific to dysphoria, whereas the Unusual Sleep Experiences factor was specific to posttraumatic stress disorder (PTSD) and dissociation. Finally, several ISDI scales showed strong evidence of specificity in relation to pathological symptoms; in particular, there were strong associations between (a) ISDI Fatigue and measures of dysphoria, (b) ISDI Nightmares and measures of PTSD, and (c) ISDI Sleep Hallucinations and measures of dissociation.