Reduction in delta activity predicted improved negative affect in Major Depressive Disorder Philip Cheng n , Jennifer Goldschmied, Melynda Casement, Hyang Sook Kim, Robert Hoffmann, Roseanne Armitage, Patricia Deldin Department of Psychiatry University of Michigan, Ann Arbor, Ann Arbor MI 48105, United States article info Article history: Received 6 March 2015 Received in revised form 12 May 2015 Accepted 29 May 2015 Available online 9 June 2015 Keywords: Depression Slow-wave sleep Affect Slow-wave disruption abstract While prior research has demonstrated a paradoxical antidepressant effect of slow-wave disruption (SWD), the specific dimensions of depression affected is still unclear. The current study aimed to extend this research by utilizing a dimensional approach in examining the antidepressant effects of SWD. Of particular interest is the affective dimension, as negative affect in depression is arguably the most salient characteristic of depression. This sample included 16 individuals with depression (10 female) recruited from the community. Participants slept in the lab for three nights (adaptation, baseline night, and SWD) with polysomnography, and completed measures of negative affect and depression severity the following morning. Results show that reduction in delta power was linearly associated with improved negative affect. Comparison of individual change scores revealed that half of the individuals showed improved negative affect, which is comparable to the reported 40–60% antidepressant response rate to sleep deprivation. Results suggest that vulnerability in the sleep homeostatic system may be a contributing individual differences factor in response to slow-wave disruption in depression. & 2015 Elsevier Ireland Ltd. All rights reserved. 1. Introduction A large body of research has implicated sleep as an important contributor to affective functioning, especially in mood disorders such as depression (Tsuno et al., 2005). Though sleep is generally positively related to affective functioning (Scott and Judge, 2006; Minkel et al., 2012), sleep deprivation appears to have a paradox- ical antidepressant effect in approximately 40–60% of individuals suffering from depression (Pflug and Tölle, 1971; Wu and Bunney, 1990). Consequently, researchers have sought to establish sleep as a viable intervention target for depression. Though the antidepressant effect of sleep deprivation is nota- ble, it subsides with recovery sleep and is therefore less viable as an intervention due to issues of sustainability and other adverse effects of chronic sleep loss. Subsequently, research has explored the value of selective disruption of slow-wave sleep as a potential mechanism for intervention (Landsness et al., 2011). Previous research has implicated abnormalities in slow-wave sleep as depressogenic (Beersma and Van den Hoofdakker, 1992), and Landsness et al. (2011) successfully demonstrated that disruptions to slow-wave activity in depression resulted in a decrease in symptom severity. While several studies have indicated that abnormalities in slow-wave sleep are characteristic of those with depression (Beersma and Van den Hoofdakker, 1992; Armitage and Hoffmann, 2001; Goldschmied et al., 2014), the specific relation- ship between slow-wave abnormalities and the various dimen- sions in the phenomenology of depression is still unclear. Conceptualizing and understanding depression utilizing a dimen- sional approach is increasingly important due to the heterogeneity in symptom presentation between individuals. The affective dimension in depression is of particular interest because it is arguably the most salient characteristic of depression, and remains a gateway criterion for a DSM-5 diagnosis of Major Depressive Disorder (i.e. presence of depressed mood for two or more weeks). Depression is also commonly examined by two distinct dimen- sions comprising of cognitive and somatic symptoms. Prior research has established differential predictive values of these two dimensions in the relationship between sleep disturbance and depression (Aloia et al., 2005). In order to further extend our knowledge about the role of sleep in depression, the current study builds upon previous research by examining how slow-wave disruption (SWD) during sleep will relate to negative affect, in addition to Somatic and Cognitive–Affective symptoms of depression. It was hypothesized Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/psychres Psychiatry Research http://dx.doi.org/10.1016/j.psychres.2015.05.037 0165-1781/& 2015 Elsevier Ireland Ltd. All rights reserved. n Correspondence to: Sleep Disorders and Research Center, Henry Ford Hospital, 39450 12 Mile Rd., Novi, MI 48377, United States. Tel.: þ1 734 926 8565; fax: þ1 248 344 8084. E-mail address: pcheng1@hfhs.org (P. Cheng). Psychiatry Research 228 (2015) 715–718