Screen time effects on sleep - Lissak, G. 2018.

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Children in 2011 were estimated to sleep, on average, one hour less per night when compared with children of the early 20th century (Magee et al., 2014). In Britain, 20-30% of young children experience sleep problems (Cheung et al., 2017). Sleep is highly important for neurodevelopment of infants and toddlers. Accumulating evidence indicates that inadequate sleep, both in duration and quality may compromise youth's physical and mental health and psychosocial functioning. Additionally, risk-taking behavior and school performance are likely to be negatively affected by inadequate sleep (Falbe et al., 2015). Sleep may also critically affect the regulation of circadian rhythms by affecting the pineal hormone melatonin, which is involved in enhancement of immune function and inhibition of development of cancer (Figueiro & Overington, 2015; Blask, 2009).

The association between digital media and sleep duration and quality relates to infancy through adolescence (Parent, Weasley-Sanders & Forehand, 2016). Novel findings suggest an inverse association between sleep duration and subsequent screen time. A longitudinal study of 4-8-year-olds found that short sleep time can promote a following-day fatigue, thus leading to more screen viewing sedentary behavior. Researchers, therefore, suggested a bidirectional association between children's length of sleep and screen time (Magee et al., 2014). An examination of all developmental stages found that sleep disturbances, when they are a result of excessive screen time, are linked to internalizing, externalizing, and peer problems (Parent et al.). Another study related to the effects of sleep on executive functioning and theory of mind (ToM) (i.e., the capacity to understand mental states, motives, and feelings of others). This study examined preschoolers and found that extensive exposure to background TV or nighttime TV viewing was associated with decreased sleep duration, consequently resulting with decreased ToM (Nathanson & Fries, 2014).

Digital media time is considered to affect sleep through the following means:

1. Displacing other activities: screen time can displace physical activity time known to be beneficiary for sleep. Additionally, screen time can come at the expense of sleep time (Cheung et al., 2017; Chahal, Fung, Kuhle & Veugelers, 2013), thus shortening sleep duration and quality (Cheung et al.; Cain & Gradisar, 2010; Magee at al., 2014). Children of lower-income families are reported to have increased TV viewing and reduced sleep quality. However, a large number of digital devices in higher socioeconomic status families could be assigned for contributing to increased screen exposure and shorter sleep time (Magee et al.)

2. Time of use: Evening and nighttime exposure to bright light and blue light emitted by self-luminous devices may suppress melatonin production, affect the timing of melatonin production and, consequently, cause circadian disruption (Cheung et al., 2017; Figueiro & Overington, 2015; Falbe et al., 2015; Cajochen et al., 2011). Bedtime access to media devices is associated with compromised sleep components of various age ranges (Carter, Rees, Hale, Bhattacharjee & Paradka, 2016). Sleep problems correspond to toddlers' evening media exposure (Garrison, Liekweg & Christakis, 2011) and to night-time access to digital devices, which according to another study seemed to have caused to fifth graders a decrease in sleep length (Chahal et al., 2013). Falbe et al. reported that use of mobile phones after bedtime by seven graders was associated with a year later report of feeling significantly more tired. Pre-adolescents and adolescents are reported to experience sleep problems particularly if they use digital media after 9:00 p.m. Additionally, extended messaging post-bedtime is likely to decrease sleep duration of high school students and to cause them daytime sleepiness and poorer academic achievements (Grover, Pecor, Malkowski & Ming, 2016). Other findings on cohorts aged 16–19 reported that over four hours of digital media use is associated with extended sleep onset latency (Hysing et al., 2017).

3. Media type – television vs. small touch-screens: the number of TV viewing hours of infants and toddlers was found related to irregularities in day naptime and bedtime onset (Thompson & Christakis, 2005). Passive TV viewing by five and six-year-olds, in particular, who were viewing adult-targeted TV programs, was found to be associated with sleep disturbances. Both active and passive viewings were found associated with sleep-wake transition disorder among 5-6-year-old children (Paavonen, Pennonen, Roine, Valkonen & Lahikainen, 2006). A more recent study added that increased passive exposure to TV was independently related with reduced daytime sleep (Cheung et al., 2017).

In contrast to TVs, small can emit audible notifications (, text messages) during sleep time, thus delaying falling asleep or causing an inadequate sleep. of adolescents were reported to be awakened by mobile phones (). Touch-screen devices were to affect toddlers aged 6–36 months as reported in a study which found a significant association between frequency of touch-screen device use (mostly tablets) which increased daytime iness (average of 10.8 minutes) and decreased night sleep (. Also, night and day sleep duration increased and night sleep onset (falling-asleep time) became longer for this population (Cheung et al., 2017).

1. Media content: exposure, primarily to video games, may increase children's psychophysiological arousal, therefore affecting sympathetic regulation (Cheung et al., 2017; Falbe et al., 2015; King, Delfabbro, Zwaans & Kaptsis, 2014). Consequently, arousal may disturb pre-bedtime relaxation and is likely to cause delayed sleep onset and shortened sleep time (Cheung et al.; Magee et al., 2014). Garrison, Liekweg, and Christakis (2013) further elaborated on the effect of violent media content on 3-5 year-olds and reported that 12 minutes of violent daytime content or 15 minutes of evening media increases the risk of inadequate sleep. Use of social media is another type of content found to affect sleep. Wood and Scott (2016) reported that adolescents' use of social media at night time predicts inadequate sleep, especially when emotional investment is involved. Moreover, the combined effect of looking at a bright mobile phone display while involved in an excitement provoking task (e.g., fast paced/violent game or worrying messaging) may increase psychophysiological arousal, thus disrupting sleep (Oshima et al., 2012).

2. Location: media devices located in children's bedroom are likely to increase overall screen exposure especially at evenings. Small sized touch-screen devices enable them to flexibly be used in children's rooms, both by the children and by parents who increasingly use such devices for interacting with their children (Northwestern University, 2014). Findings by Brambilla et al. (2017) suggested that children's use of electronic media devices in the bedroom is related to decrease in sleep duration. The number of media devices owned by adolescents, particularly when located in the bedroom, was related to delayed bedtimes, shorter sleep duration, increased bedtime resistance, and a higher level of sleep disturbance (Bruni et al., 2015; Hysing et al., 2017).

3. Electromagnetic radiation is sensed as light: The pineal gland, producing melatonin, may sense electromagnetic radiation as light. Therefore exposure to electromagnetic radiation from wireless devices may delay melatonin production, thus affecting sleep (Halgamuge, 2013).