ORIGINAL INVESTIGATION Hyperstable regulation of vigilance in patients with major depressive disorder ULRICH HEGERL ∗ , KATHRIN WILK ∗ , SEBASTIAN OLBRICH, PETER SCHOENKNECHT & CHRISTIAN SANDER Department of Psychiatry and Psychotherapy, University Hospital Leipzig, Leipzig, Germany Abstract Objectives. This study tested the hypothesis that patients with depression show less and later declines into lower EEG vigilance stages (different global functional brain states) under resting conditions than healthy controls, as proposed by the vigilance theory of affective disorders. Methods. Thirty patients with Major Depressive Disorder (19 female; mean age: 37.2 years, SD: 12.6) without psychotropic medication and 30 carefully age- and sex-matched controls (19 female; mean age: 37.3 years, SD: 12.8) without past or present mental disorders underwent a 15-min resting EEG. EEG-vigilance regulation was determined with a computer-based vigilance classification algorithm (VIGALL, Vigilance Algorithm Leipzig), allowing a classification of vigilance stages A (with substages A1, A2 and A3), B (with substages B1 and B2/3) and C. Results. Depressive patients spent significantly more time in the highest EEG vigilance substage A1, and less time in substages A2, A3 and B2/3 than controls. In depressive patients, a significantly longer latency until the occurrence of substages A2, A3 and B2/3 was observed. No significant group differences in the percentage of B1 segments or the latency until occurrence of B1 were found. Conclusions. The results confirm the hypothesis that patients with depression show less (and later) declines into lower EEG vigilance stages under resting conditions than healthy controls, and support the vigilance theory of affec- tive disorders linking a hyperstable vigilance regulation to depression. Key words: Affective disorders, major depressive disorder, EEG, vigilance, VIGALL Introduction Major depressive disorders (MDD) and Bipolar Affective Disorders (BD) with manic and depressive episodes are severe and prevalent disorders. Several features of these affective disorders, e.g. the some- times rapid onset of manic and depressive episodes (especially in bipolar depression) (Hegerl et al. 2008a), the rapid switches between episodes (Feldman- Naim et al. 1997; Wilk and Hegerl 2010) and the rapid response to sleep deprivation (Wu and Bunney 1990; Giedke and Schwarzler 2002), suggest the existence of circumscribed pathogenetic mecha- nisms with strong biological underpinnings. Electro- encephalography (EEG) and especially quantitative EEG have long been used to identify biomarkers of depressive disorders (Pollock and Schneider 1990; Hunter et al. 2007; Steiger and Kimura 2010). Con- cerning the wake resting EEG, a general increase in alpha power (Pollock and Schneider 1990) and hemispheric asymmetry (e.g., Bruder et al. 2001; Davidson et al. 2002) are typical findings in depres- sive patients. Furthermore, several EEG features, such as an increased pretreatment alpha activity (Ulrich et al. 1984; Bruder et al. 2008), pretreat- ment delta and theta activity (Knott et al. 1996, 2000; Iosifescu et al. 2009; Spronk et al. 2011) or changes in theta cordance (Cook et al. 2002, 2009; Bares et al. 2008, 2010) were shown to be useful in predicting treatment response. So far, most reported studies lack a convincing theoretical expla- nation for the EEG characteristics of patients with depressive disorders. Recently a theory of the pathogenesis of affective disorders was proposed (Hegerl et al. 2009) that attributes an important pathogenetic role to the regulation of vigilance. Noteworthy, here the term “vigilance” labels not processes involved in the “sus- tained attentional monitoring of the environment”. ∗ Shared first authorship. Correspondence: Kathrin Wilk, Department of Psychiatry and Psychotherapy, University Hospital Leipzig, Semmelweisstrasse 10, 04103 Leipzig, Germany. Tel: + 49 341 9724547. Fax: + 49 341 724539. E-mail: kathrin.wilk@medizin.uni-leipzig.de (Received 22 October 2010; accepted 5 April 2011) The World Journal of Biological Psychiatry, 2011; Early Online, 1–11 ISSN 1562-2975 print/ISSN 1814-1412 online © 2011 Informa Healthcare DOI: 10.3109/15622975.2011.579164 World J Biol Psychiatry Downloaded from informahealthcare.com by UB Leipzig on 07/08/11 For personal use only.