Revisiting the factor structure of the insomnia severity index among survivors of the 2013 Super Typhoon Haiyan.

Abstract

<p><strong>Objective: </strong>The insomnia severity index (ISI) is often used as a screening tool used with its recommended clinical cutoff scores. However, this practice presumes a single-factor structure, which has received little theoretical or empirical support. This study examined the factor structure of the ISI with the aim to validate its clinical application in postdisaster contexts.</p><p><strong>Method: </strong>One hundred sixty-eight Filipino adult survivors of the 2013 Super Typhoon Haiyan completed two waves of questionnaires that were 7 months apart. Confirmatory factor analyses were first conducted to compare models with different factor structures, followed by a test of longitudinal measurement invariance. The longitudinal interrelations among factors of the ISI as well as between insomnia and symptoms of psychological distress were then examined with path analysis.</p><p><strong>Results: </strong>Results supported a two-factor model, composed of <em>severity</em> and <em>impact</em> of insomnia, which achieved strong longitudinal invariance. The change in <em>impact</em> of insomnia at T2 was predicted by <em>severity</em> of insomnia at T1. <em>Impact</em> of insomnia was significantly associated with symptoms of stress but not depression and anxiety.</p><p><strong>Conclusion: </strong>We preliminarily propose a model in which the <em>impact</em> of insomnia mediates the influence of <em>severity</em> of insomnia on subsequent stress.</p>