Erin Koffel

Further Validation of the Iowa Sleep Disturbances Inventory

Erin Koffel — Sun, 23 Oct 2011 11:13:34 PDT

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.

Unusual sleep experiences, dissociation, and schizotypy: Evidence for a common domain.

Erin Koffel et al. — Thu, 20 May 2010 16:51:03 PDT

This paper reviews studies that have examined associations between unusual sleep experiences (including nightmares, vivid dreaming, narcolepsy symptoms, and complex nighttime behaviors) and dissociation and schizotypy. Using correlational studies and structural analyses, evidence is provided that unusual sleep experiences, dissociation, and schizotypy belong to a common domain. It is demonstrated that unusual sleep experiences show specificity to dissociation and schizotypy compared to other daytime symptoms (e.g., anxiety, depression, substance use) and other sleep disturbances (e.g., insomnia, lassitude/fatigue). The paper also outlines the methodological limitations of the existing evidence and makes suggestions for future research. Finally, three models for the overlap of daytime and nighttime symptoms are reviewed, including biological abnormalities, trauma, and personality traits. Although further research is needed, it is suggested that daytime and nighttime symptoms result from problems with sleep-wake state boundaries, which may be precipitated by stress or trauma. In addition, association between daytime and nighttime symptoms can be attributed to the higher order personality trait of Oddity.

Iowa Sleep Disturbances Inventory (ISDI)

Erin Koffel — Thu, 20 May 2010 16:51:02 PDT

The Iowa Sleep Disturbances Inventory (ISDI) can be used to measure a wide range of sleep disturbances. Please contact the author for validation information.

Further validation of the IDAS: Evidence of Convergent, Discriminant, Criterion, and Incremental Validity

David Watson et al. — Mon, 06 Apr 2009 10:19:38 PDT

We explicated the validity of the Inventory of Depression and Anxiety Symptoms (IDAS; Watson et al., 2007) in two samples (306 college students, and 605 psychiatric patients). The IDAS scales showed strong convergent validity in relation to parallel interview-based scores on the Clinician Rating version of the IDAS (IDAS-CR); the mean convergent correlations were .51 and .62 in the student and patient samples, respectively. With the exception of Well-Being, the scales also consistently demonstrated significant discriminant validity. Furthermore, the scales displayed substantial criterion validity in relation to DSM-IV mood and anxiety disorder diagnoses in the patient sample. We identified particularly clear and strong associations between (a) major depression and the IDAS General Depression, Dysphoria and Well-Being scales; (b) panic disorder and IDAS Panic; (c) posttraumatic stress disorder and IDAS Traumatic Intrusions; and (d) social phobia and IDAS Social Anxiety. Finally, in logistic regression analyses, the IDAS scales showed significant incremental validity in predicting several DSM-IV diagnoses when compared against the Beck Depression Inventory-II (Beck, Steer, & Brown, 1996) and Beck Anxiety Inventory (Beck & Steer, 1990).

The Two-Factor Structure of Sleep Complaints and Its Relation to Depression and Anxiety

Erin Koffel et al. — Mon, 06 Apr 2009 10:18:49 PDT

Although sleep complaints are common in depression and anxiety, there is little agreement as to how they should be organized and assessed. It is also unclear whether sleep complaints show specificity with certain disorders or if they are nonspecific symptoms. We examined the structure of sleep complaints and the relations of these complaints to depression and anxiety in three samples: college students, older adults, and psychiatric patients. Exploratory and confirmatory factor analyses indicated that sleep complaints consistently defined two distinct dimensions: Insomnia and Lassitude. The Insomnia factor included indicators of early, middle, and late insomnia, as well as poor sleep quality. The Lassitude factor included measures of hypersomnia, fatigue, and sleepiness. Both factors were significantly related to symptoms and diagnoses of depression and anxiety. However, Lassitude was more strongly related to symptoms of depression and anxiety than was Insomnia. In addition, Lassitude showed specificity to measures and diagnoses of depression compared to anxiety disorders. This specificity can be explained by Lassitude’s relation with negative and positive emotionality, both of which are components of depression.