title: Schizophrenia and depression: The relation between sleep quality and working memory.
abstract: Sleep is known to be markedly disturbed in patients with depression, but in patients with schizophrenia these problems are underestimated. This research aimed to determine if a relationship existed between sleep problems in patients with schizophrenia and with depression and their reduced working memory (WM) performance. Thirty outpatients with schizophrenia, 30 outpatients with depression, and 30 healthy control participants were enrolled in this study. All participants completed a sleep questionnaire (i.e., Pittsburgh Sleep Quality Index (PSQI)), two simple WM tasks tapping only its storage component (i.e., digit span forward and backward task), and two complex WM tasks tapping both its storage and processing components (i.e., letter-number sequencing and reading span task). The results showed that neither psychiatric group differed from the healthy controls on simple WM tasks. Patients with schizophrenia did not differ from those with depression in the performance of simple or complex WM tasks. However, patients with schizophrenia, and, to a lesser degree, patients with depression performed significantly worse than the healthy control participants on complex WM tasks, which was visible in lower WM scores for patients with depression and in slower information processing, as well, for patients with schizophrenia. Finally, a significant negative relationship was found between the PSQI score and the reading span task scores; thus, participants with worse performance tended to report more sleep problems. To conclude, sleep needs to receive more priority when treating patients with depression and especially patients with schizophrenia because better sleep improves (working) memory performance and daily functioning.
authors.affiliation: Research Group of Pain and Neuroscience, Kyung Hee University, #47 Gyeonghuidae-Gil, Dongdaemun-Gu, Seoul 130-701, Republic of Korea; Brussels Institute for Applied Linguistics, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium. Electronic address: info@mauritsvandennoort.com.
authors.forename: Maurits van den
authors.initials: MV
authors.lastname: Noort
authors.affiliation: Center of Linguistics, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium. Electronic address: estruys@vub.ac.be.
authors.forename: Esli
authors.initials: E
authors.lastname: Struys
authors.affiliation: Department of Psychology, Université de Fribourg, Rue de Faucigny 2, 1700 Fribourg, Switzerland. Electronic address: benoit.perriard@unifr.ch.
authors.forename: Benoît
authors.initials: B
authors.lastname: Perriard
authors.affiliation: Psychiatric Research Institute, LVR-Klinik Bedburg-Hau, Nassauerallee 93-97, 47533 Kleve, Germany. Electronic address: Heike.Staudte@lvr.de.
authors.forename: Heike
authors.initials: H
authors.lastname: Staudte
authors.affiliation: Department of Acupuncture & Meridian of Oriental Medicine, Sang Ji University, 83 Sangjidae-gil, Wonju 26339, Republic of Korea. Electronic address: pinkteeth@daum.net.
authors.forename: Sujung
authors.initials: S
authors.lastname: Yeo
authors.affiliation: Research Group of Pain and Neuroscience, Kyung Hee University, #47 Gyeonghuidae-Gil, Dongdaemun-Gu, Seoul 130-701, Republic of Korea. Electronic address: lims@khu.ac.kr.
authors.forename: Sabina
authors.initials: S
authors.lastname: Lim
authors.affiliation: Research Group of Pain and Neuroscience, Kyung Hee University, #47 Gyeonghuidae-Gil, Dongdaemun-Gu, Seoul 130-701, Republic of Korea; Psychiatric Research Institute, LVR-Klinik Bedburg-Hau, Nassauerallee 93-97, 47533 Kleve, Germany; Donders Institute for Brain, Cognition, and Behaviour, Centre for Cognition, Radboud University Nijmegen, Montessorilaan 3, 6525 HR Nijmegen, The Netherlands, The Netherlands. Electronic address: p.bosch@donders.ru.nl.
authors.forename: Peggy
authors.initials: P
authors.lastname: Bosch
mesh_terms: D000328:Adult; D003863:Depression / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D012559:Schizophrenia / Q000503:physiopathology*; D012893:Sleep Wake Disorders / Q000503:physiopathology*
keywords: Depression; Reading span task; Schizophrenia; Sleep quality; Working memory