Habitual computer game playing at night is related to depressive symptoms Sakari Lemola a,b,⇑ , Serge Brand c , Nicole Vogler a , Nadine Perkinson-Gloor a , Mathias Allemand d , Alexander Grob a a University of Basel, Department of Psychology, Basel, Switzerland b University of Helsinki, Faculty of Behavioural Sciences, Helsinki, Finland c Psychiatric Hospital of the University of Basel, Basel, Switzerland d University of Zürich, Department of Psychology, Zürich, Switzerland article info Article history: Received 20 September 2010 Received in revised form 9 March 2011 Accepted 16 March 2011 Available online 8 April 2011 Keywords: Depression Computer game playing Circadian rhythms Sleep duration Sleep problems Daytime sleepiness Adolescence Young adulthood abstract This study investigated whether the amount and circadian time of habitual computer game playing were related to depressive symptoms in adolescents and young adults. We expected that habitual late playing relates to more depressive symptoms beyond the effect of the total time of computer game playing as playing at night may involve short, irregular, and disturbed sleep as well as misalignment of the circadian rhythm. 646 adolescents and young adults (ages 13–30; 90.9% males) who play the internet role-playing game World of Warcraft completed an online questionnaire. Habitual computer game playing between 10 pm and 6 am was related to an increased risk of high depression scores independent of the total amount of playing. Adolescents (ages 13–17 years) were most vulnerable when habitually playing during early night (i.e., 10–12 pm), while emergent adults (ages 18–22 years) showed more vulnerability when habitually playing late at night (i.e., after 2 am). The effect was partly mediated by daytime sleepiness but not by sleep loss or insomnia problems. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Short, irregular, and disturbed sleep, as well as problems of cir- cadian rhythmicity are related to poor adjustment particularly dur- ing adolescence and young adulthood (Roberts, Roberts, & Duong, 2008; Shirayama et al., 2003; Wolfson & Carskadon, 1998). High school students with short sleep on school-nights reported in- creased levels of depressed mood and daytime sleepiness in com- parison to individuals who sleep longer (Wolfson & Carskadon, 1998). Further, late bedtimes were associated with higher inci- dence of depressive symptoms and suicidal ideation (Gangwisch et al., 2010). In a related vein, individuals with delayed sleep phase syndrome are at increased risk for mental health problems (Okawa & Uchiyama, 2007; Shirayama et al., 2003). These sequels may con- stitute a vicious circle and perpetuate sleeping difficulties and desynchronization of the circadian rhythm. Indicative of a causal mechanism, studies show mental health and well-being to improve when the circadian rhythm gets normally entrained to the exogenous day–night cycle by oral melatonin treatment (Rah- man, Kayumov, & Shapiro, 2010). The present study aims at examining the interplay of computer game playing during the night, sleep patterns, and depressive symptoms. According to every day experience of parents and teachers excessive computer game playing and in particular habit- ual playing late at night have a detrimental impact on psychologic functioning. Moreover, psychologists and pediatricians are nowa- days often confronted with children and adolescents suffering from addictive computer game playing. In a representative study of more than 15,000 9th graders in Germany, 15.8% of the adolescent boys and 4.3% of the girls play computer games for more than 4.5 h per day and 3% of the boys and 0.3% of the girls can be considered as addicted to computer games according to ICD-10 derived crite- ria (Rehbein, Kleimann, & Mössle, 2010). The computer game with the highest addiction risk was the Massively Multiplayer Online Role-Playing Game (MMORPG) World of Warcraft (WoW). MMORPGs are competitive role-playing games normally played in cooperative groups. These groups gather for online-playing appointments and, as the success of the whole group depends on the collaboration of all group members, individual players are pressured to join the gatherings, which may explain the addic- tive potential (Bessière, Seay, & Kiesler, 2007). MMORPGs are 0191-8869/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.paid.2011.03.024 Abbreviations: WoW, World of Warcraft; MMORPG, Massively Multiplayer Online Role-Playing Game; ADS-K, short version of the ‘Allgemeine Depressionsskala’. ⇑ Corresponding author. Address: Missionsstrasse 62a, 4055 Basel, Switzerland. Tel.: +41 61 267 0638; fax: +41 61 267 0661. E-mail address: sakari.lemola@unibas.ch (S. Lemola). Personality and Individual Differences 51 (2011) 117–122 Contents lists available at ScienceDirect Personality and Individual Differences journal homepage: www.elsevier.com/locate/paid