*3.4. Studies on the E*ff*ects of Artificial Light Sources on Adolescents*

Several authors [56–59], have referred for years to the problem of mobile phone addiction, which they define in different ways as mobile phone dependence, the problematic use of mobile phones or cell phones, mobile phone abuse, and nomophobia (a fear of being without one's phone). Symptoms include preoccupation with the device, excessive use with loss of control, use of the device in inappropriate or dangerous situations, adverse effects on relationships, symptoms from lack of use (feeling angry, tense, depressed when the mobile phone is not accessible, constantly worrying that the battery will run out, etc.), and tolerance symptoms (the need for a better mobile phone, more software, or more hours of use). These symptoms are similar to those of substance dependence, which is why some researchers consider mobile phone dependence (MPD) to be an independent diagnosis.

A study was carried out in 2015 that surveyed 415 secondary school adolescents, among whom 251 were boys (60.48%) and 164 were girls (39.51%). The average age of the participants was 13.99 ± 0.8 years. The average time spent each day with a mobile phone was 131.77 ± 119.9 min. In this way, the prevalence of mobile phone dependence was demonstrated. Indian boy and girl adolescents comprised 33.5% and 39.6% of the study, respectively, and it was conducted using the International Classification of Diseases 10th edition (ICD-10), classification criteria for mental and behavioral disorder dependence syndromes [60].

LeBourgeois et al. [61] published an article on the effects of machine-emitted light on physiological circadian and warning sleep timers. They claimed that a high percentage of young people and adolescents have insufficient sleep periods. They referred to a 2004 article entitled "National Sleep Foundation. Sleep in America poll: Teens and Sleep", in which a large majority of studies were shown to find an adverse association between electronics consumption and sleep health, as well as a short time in bed and reduced sleep time. U.S. population data show that approximately 30% of preschool children and between 50% and 90% of school-age children and adolescents do not sleep as much as they need to. Data from a study of 454 teenagers revealed that more than 60% go to bed with their mobile phones and more than 45% use their mobile phone as an alarm or as a light. In addition, recent studies of 2000 students in grades four through six indicated that sleeping close to what is defined as "a small screen" was associated with increased fatigue.

Additionally, Crowley et al.'s [62] recent findings indicate that prepubescent children compared to postpubescent adolescents have greater melatonin suppression under low (15 lx), moderate (150 lx), and bright (5000 lx) light exposure in the hours prior to bedtime. Turner and Mainster [63] stated that children are more sensitive to light than adults based on their eye structures featuring a larger pupil size and a higher lens transmission.

Another study was conducted on 9846 adolescents between the ages of 16 and 19, taking into account the type and frequency of electronic equipment used in bed and the hours spent in front of screens during rest time. Sleep variables were calculated based on time in bed, duration of sleep, latency time before sleep, and state upon waking after sleep. The results of the study confirm that the adolescents spent a great deal of time during the day and in bed using electronic equipment. The use of electronic devices during the day and night was associated with an increased risk of a short sleep duration, a long sleep onset latency, and increased sleep deficits. The conclusion of the study is that the frequent use of electronic equipment is as common in adolescents during the day as it is at night. These results demonstrate a negative relationship between the use of technology and sleep, suggesting that recommendations on healthy use could involve a restriction of device usage [64].

A total of 746 surveys were conducted by Feizhou Zheng et al. [65] with children in Chongqing, China between October 2011 and May 2012 with data such as mobile phone use, if they feel well, and other possible confounding factors. Fatigue was significantly associated with years of mobile phone use and daily call duration. Headache was also significantly associated with daily call duration. There was no significant association between mobile phone use and other physical symptoms in the children and no consistent association with fatigue. The Independent Expert Group on Mobile Phones (IEGMP) reported several possible reasons for such sensitivity, including the information below.


Yoshimura et al. [66] conducted a study on the mobile phone use of 23 nursing students. The measurements of the mobile devices showed the peak light of the mobiles at 453 nm, and the values of illuminance produced by each of the mobile devices were 25.3 to 42.6 lx (simulating their use in a seated position) and 50.5 to 80.4 lx (lying down).

Bae [67], in an editorial in a Korean journal of medicine in 2017, referred to several studies on the mobile phone dependency of adolescents. Min referred to an article by Lin et al. [68], which stated that dependence on smartphones is a problem that has spread throughout the world and, based on the study, proposed diagnostic criteria for smartphone addiction. Min also referred to a study by Elhai et al. [69] that related the use of smartphones to anxiety and psychopathological depression. In the editorial, Min states that the studies being published allude to various physical and psychological problems, including ophthalmological, orthopedic, and sleep disorders due to the use of smartphones. This supports the claim that adolescents are a group at higher risk for addiction because of their developing brains, as stated in the National Information Society Agency (KR) study, "Survey on smartphone overuse" (2017) and in Long J et al. [70].

On 5 October 2017, the Spanish National Statistics Institute (INE) published the "Survey on Equipment and Use of Information and Communication Technologies in Households. Year 2017". The statistics show that the proportion of children (from 10 to 15 years old) who use information and communications technology (ICT) is, in general, very high. Thus, the use of computers among children is very widespread (92.4%) (even more so for the use of the internet (95.1%)). In 2016, the number of minors using the internet exceeded the number of those using a computer. The differences by sex were not very significant. By age, the results suggested that the use of computers and the internet was a majority practice among children aged ≤ 10 years old. In turn, the use of mobile phones was found to increase significantly (Table 2) after the age of 10, reaching 94.0% in the population aged 15 years old [71].


**Table 2.** Percentage of underage information and communications technology (ICT) users among children aged 10–15 years. Percentage of underage ICT users by gender and age [71].
