title: Further validation of the Iowa Sleep Disturbances Inventory.
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 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 Insomnia and Lassitude factors 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.
authors.affiliation: Department of Psychology, E11 Seashore Hall, University of Iowa, Iowa City, IA 52242-1407, USA. erin-koffel@uiowa.edu
authors.forename: Erin
authors.initials: E
authors.lastname: Koffel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004213:Dissociative Disorders / Q000150:complications / Q000523:psychology; D004834:Epilepsy, Post-Traumatic / Q000150:complications / Q000523:psychology; D005260:Female; D006801:Humans; D007407:Interviews as Topic / Q000592:standards; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D015203:Reproducibility of Results; D012569:Schizotypal Personality Disorder / Q000150:complications / Q000523:psychology; D012893:Sleep Wake Disorders / Q000150:complications / Q000175:diagnosis*; D011795:Surveys and Questionnaires / Q000592:standards; D055815:Young Adult