Examining the effects of sleep delay on depressed males and females and healthy controls JENNIFER R. GOLDSCHMIED, PHILIP CHENG, ROSEANNE ARMITAGE and PATRICIA J. DELDIN Department of Psychology, University of Michigan, Ann Arbor, MI, USA Keywords sex effects, slow wave activity, sleep regulation Correspondence Jennifer Goldschmied, MS, Department of Psychology, University of Michigan, 530 Church Street, Ann Arbor, MI 48109, USA. fax: 734-615-0573; e-mail: jrgolds@umich.edu Accepted in revised form 10 May 2014; received 21 February 2014 DOI: 10.1111/jsr.12174 SUMMARY Individuals with major depressive disorder typically exhibit sleep electroencephalograpy abnormalities which have been shown to vary by sex. Recent research has shown that depressed males display deficits in slow wave sleep and delta electroencephalograph (EEG) activity that are not apparent in depressed females. This may suggest that males and females with depression vary with respect to their homeostatic regulation of sleep. Utilizing archival data, the present study examined the effects of a 3-h sleep delay, which represents a mild sleep challenge, on slow wave activity in healthy controls and individuals with depression. All participants slept in the laboratory for three sequential nights. On the third night in the laboratory, the participants’ bedtime was delayed by 3 h. Slow wave activity was calculated utilizing power spectral analysis and compared across groups. Following the sleep delay, males with depression exhibited the lowest slow wave activity compared to all other groups. These results may suggest that males with depression are at a greater risk for homeostatic dysregulation than females, and may require specialized intervention. INTRODUCTION Sleep disturbance is one of the central symptoms reported by most individuals with major depressive disorder (MDD; Mendlewicz, 2009). Years of research looking at differences in sleep between healthy subjects and those diagnosed with MDD have greatly increased our understanding of the qualitative difference in sleep in those with MDD. With regard to the most common differences in visually scored sleep variables, research has shown consistently that individuals with MDD have more proportionate time awake, a measure of sleep efficiency, shorter time to enter REM sleep (REM latency), greater amount of REM sleep, increased amounts of rapid eye movements (REM density) and decreases in slow wave sleep compared to healthy controls. Understanding these qualitative differences has been an essential first step; however, newer methodology, including quantitative electro- encephalograph (EEG) analysis, may allow us to assess more clearly the differences in sleep regulation in MDD. Borb ely and Wirz-Justice (1982) suggested that the sleep disturbances occurring in individuals with MDD, including delayed sleep onset and difficulty maintaining sleep, were a result of a reduced drive for sleep (process S). This model also suggests that those with MDD would present reduced slow wave sleep during the first portion of the night, when slow wave activity is typically at its highest. Kupfer et al. (1986) demonstrated that there was indeed a reduction in slow wave EEG activity in NREM sleep (SWA) in those with MDD; however, they also noted that there was only a very small relationship between time awake and reduced delta activity in those with MDD. Utilizing quantitative EEG analy- ses, Armitage et al. (1992, 1995, 1997, 2000a,b) have also shown that individuals with MDD exhibit an abnormal distribution of SWA across the night. These findings suggest that those with MDD exhibit greater dysfunction than origi- nally theorized with respect to physiological functioning, including homeostatic regulation. Research into the function of SWA has shown that SWA increases proportionately to the amount of prior wakefulness and dissipates rapidly over NREM sleep time (Borb ely, 1981). Moreover, how quickly SWA asymptotes after sleep onset is presumed to reflect the basic sleep drive, whereas SWA dissipation has been taken as a proxy for neuronal recovery function. In order to explore SWA regulation and its relationship to homeostatic functioning it is necessary to utilize a sleep manipulation, such as sleep deprivation, to challenge the system. A 3-h sleep delay, as described in Armitage et al. (2007, 2012), has been utilized successfully ª 2014 European Sleep Research Society 664 J Sleep Res. (2014) 23, 664–672 Depression and sleep