Relationship between internet addiction and sleep disturbance in high school students: a cross-sectional study

The Internet is a network that connects information devices across the world to provide convenient information and communication technology that enables various activities, ranging from exchanging electronic mail and information to shopping. In 2016, when this study was conducted, 48% of all people worldwide used the Internet [1]. In this context, a large survey of Japanese youth found that 6.2% of boys and 9.8% of girls presented problematic Internet use [2].

Internet addiction (IA) has been defined as “an impulse-control disorder that does not involve an intoxicant” [3]. This survey examined the concept of IA. Generalized IA is a concept that was initially introduced by Davis et al. [4] based on a cognitive-behavioral model. More recently, a meta-analysis of 89,281 individuals in 31 countries from 1996 to 2012 reported an IA prevalence of 6%, with a median age of 18.42 years (standard deviation [SD], 5.02; range, 12–41) [5]; individuals aged between 15 and 24 years account for approximately 25% of Internet users worldwide [1]. Moreover, this age range includes adolescents, which means that policies regarding IA must consider this population.

A previous study on IA among adolescents reported a significant relationship between this addiction and psychiatric disturbances, including “interpersonal sensitivity,” “depression,” “anxiety,” “hostility,” and “psychoticism.” [6]. Furthermore, adolescent IA has been reported to be a risk factor for problematic alcohol use in adulthood [7, 8]. Recent studies using functional magnetic resonance imaging have reported that IA is related to structural and functional damage in the prefrontal cortex [9]. With such severe negative impacts on life, the seriousness of this problem has been increasingly recognized, and several epidemiological studies have been conducted to determine factors related to IA. For example, a study that examined the data of 100,000 Japanese youth found that IA was related to the frequency and amount of alcohol consumption [10]. A study of 2620 Chinese high school students reported a relationship between IA and emotional anxiety and a lack of empathy [11]. Excessive smartphone use may be associated with musculoskeletal discomfort and mental health problems [12, 13].

For adolescents, sleep behavior is a component of daily life that has a major impact on physical and mental health [14]. Moreover, adolescent sleep is important because of its significant effects on the development of vital psychophysiological functions, including behavior, emotions, and attention [15‐21]. Therefore, it is important to investigate the relationship between sleep and IA. Some studies have reported an association between IA and depression and sleep disturbance [22, 23], nighttime sleep duration and subjective insomnia [24], poor sleeping habits [25], smartphone dependence [26], and sleep quality [27]. Sleeping habits are associated with other lifestyle habits, such as extracurricular activities and skipped meals [28, 29]. However, the relationship between IA and sleep disturbance in adolescents has not yet been comprehensively investigated, because few large-scale surveys have been undertaken using standard indicators, such as the Pittsburgh Sleep Quality Index (PSQI) [30].

We hypothesized that sleep disorders in puberty are associated with a general degree of Internet dependence and that this association is also attributable, in part, to other lifestyle habits. It is important to take lifestyle habits into account, because they can weaken the relationship between sleep disorders and Internet dependence. Therefore, we conducted an epidemiological study to determine the relationship between IA and sleep disturbance in Japanese high school students.

Figure 1 shows a flowchart of the participant-selection process. Of the 54 schools (with a total of 10,405 students) that were requested to participate, 40 schools agreed to participate. At the time of the study, there were 7186 first-year (of the 3-year program) high school students, of whom 6950 provided informed consent or their parents provided consent (response rate: 96.7%). Of these, 5264 students (2635 boys and 2629 girls) completed the J-PSQI and-J-YDQ (effective response rate: 73.3%).

Figure 2 shows the distribution of J-PSQI and YDQ scores. The J-PSQI scores for boys and girls were symmetrically distributed around a cutoff point value of 5.5 points. The mean and SD of the total J-PSQI score was 5.51 ± 2.63 (range: 0–17) and 5.98 ± 2.62 points (range: 0–18) for boys and girls, respectively. Regarding the YDQ scores, 0 was the most frequent score for both boys and girls. However, the point distribution varied by gender. Among boys, the number of points decreased as the score increased. Conversely, among girls, the score remained constant among those with 0 to 3 points and then gradually decreased as the number of points increased.

Table 1 shows the prevalence of students with sleep disturbance and the number of participants included in each of the three YDQ categories. Students defined as having sleep disturbance comprised 50.5% of all participants. In boys and girls, we observed a higher percentage of sleep disturbance in the following student groups: private high school students (p < 0.05), and those with a long school-commute time (p < 0.01), a high frequency of skipped meals per week (p < 0.001), depressed mood (p < 0.001), or poor school-life satisfaction (p < 0.001). Furthermore, boys spent little time engaging in school sports (or club) activities (p < 0.001). Regarding IA, the proportion with a YDQ score ≥ 5 and YDQ score of 3–4 was higher in girls than boys. In both boys and girls, the prevalence of IA was high in those with less than one-hour of school sport or club activity, more than seven skipped meals a week (p < 0.001), depressed mood (p < 0.001), and poor school-life satisfaction (p < 0.001). Additionally, the prevalence of IA was higher among girls who had shorter extracurricular learning time (p < 0.001). The relationship between television-viewing time and IA differed according to gender. The percentage of boys with a YDQ score ≥ 5 was higher among those who watched TV for ≥3 h per day. Conversely, the percentage of girls with a YDQ score ≥ 5 was higher among those who watched TV for ≤1 h per day.

Table 2 shows the prevalence of students with sleep disturbance for each of the three categories of YDQ. In both boys and girls, students categorized as having IA, or at risk of developing IA, had a higher prevalence of sleep disturbance.

Table 3 shows the multiple logistic regression analysis of the relationship between YDQ categories and sleep disturbance. In both boys and girls, the there was a statistically significant association between sleep disturbance and IA (Table 3). As compared to boys with YDQ scores ≤2, boys with YDQ scores of 3–4 and those with YDQ scores ≥5 had an increased likelihood of sleep disturbance (OR: 2.17, 95% CI: 1.80–2.61; and OR: 3.76, 95% CI: 2.82–5.01, respectively). Similarly, as compared to girls with YDQ scores ≤2, girls with YDQ scores 3–4 and those with YDQ scores ≥5 had an increased likelihood of sleep disturbance (OR: 2.20, 95% CI 1.84–2.64; and OR: 4.53, 95% CI: 3.48–5.88, respectively) The association between the YDQ scores and sleep disturbance remained significant (p < 0.001) after adjustment for potential confounding variables.

This study aimed to clarify the relationship between sleep disturbance in adolescents and IA in one prefecture in Japan. We found an association between adolescent sleep disturbance and IA with sleep disturbance being more prevalent in boys and girls with higher YDQ scores. The results of the multivariate analysis revealed a significantly higher odds of sleep disturbance in students with high YDQ scores.

Despite the importance of adolescent sleep, sleep disturbance was present in more than half of the study participants. The high proportion of adolescents with sleep disturbance is in accordance with the results of recent studies of older adolescents using the PSQI [47, 48]. In this study, sleep disturbance was more frequent among students who did not participate in school sports or clubs, skipped meals, had depressed moods, and were dissatisfied with school-life. These results were similar to those of previous studies linking regular sleep habits to psychological and physical health [14]. Additionally, the prevalence of sleep disturbance was higher among students attending private schools and students with longer commutes. In general, students attending private schools tend to have longer commutes; therefore, they may have less sleep as has been shown previously [49]. Previous studies have suggested that sleep quality is related to health and emotions among youth [14, 50]. Future longitudinal studies should examine secular changes in these and other variables in order to improve the understanding of the relationship between sleep disturbance and Internet dependence.

Boys and girls who performed less than one school sport or club activity comprised the highest proportion of students with J-YDQ scores ≥5, providing evidence of a relationship between inactivity and IA. Additionally, students who skipped more than seven meals per week had a significantly higher likelihood of IA. Similar to previous studies [23, 26], the association of IA with exercise and diet was associated with a lack of a daytime routine. The proportion of high YDQ scores for extracurricular learning and TV viewing time differed between girls and boys. This may be attributable to gender-related differences in lifestyle and IA onset. In the multiple logistic regression analysis of the relationship between J-YDQ categories and sleep disturbance, the OR decreased after adjusting for lifestyle factors. Sleep disturbance and IA are associated with various lifestyle factors [23, 26]; therefore, this relationship needs further investigation. Future longitudinal surveys can be used to facilitate the development of health education programs to reduce the prevalence of sleep disturbance and Internet dependence.

The association between the YDQ scores and sleep disturbance is similar to that reported by Bakken et al. [51] from a study among Norwegians, aged ≥16 years in which participants with high YDQ scores had a significantly higher prevalence of sleep disturbance than non-problematic Internet users. Furthermore, this study found differences according to gender, with a stronger association between sleep disturbance and girls than in boys. This finding is similar to the results of a study by Durkee et al. [25], which found a significant relationship between insufficient sleep and IA in girls.

There are several possible mechanisms for the relationship between sleep disturbance and IA. First, a study by Tan et al. [22] found that IA could cause sleep disturbances. Moreover, Chen et al. [30] indicated that IA was associated with a disturbed circadian rhythm, leading to sleep disturbance.

Conversely, a second possible mechanism is that sleep disturbance might lead to the development of IA. In a longitudinal study, Chen et al. reported that falling asleep and nocturnal awakening difficulties were predictors of IA [30].

A third possible mechanism is that both conditions contribute to each other. Several studies on adults using brain imaging have confirmed that sleep disturbance and IA cause changes in the gray matter [52, 53]. A study of retired military personnel showed that individuals with a high PSQI score presented with a reduced volume of the entire cortex and frontal lobes, regardless of their mental health [53]. Another study that did not control for sleep disturbance reported that individuals with IA had reduced gray matter density [52]. These findings suggest that IA may cause organic (structural) changes in sleep-related neural pathways.

This study has the following three strengths: First, the sample size was adequate to ensure statistical power. Second, to investigate the relationship between sleep disturbance and IA, we used the PSQI and YDQ, which have been frequently used as standard indices in several epidemiological surveys [5, 10, 25, 39, 41, 43, 51, 52, 54‐59]. Third, in our analysis, we evaluated the relationships between sleep disturbance and IA for each of the three categories of the YDQ, including at-risk Internet use.

This study also had several limitations. First, study was a cross-sectional survey, so it is not possible to formulate any conclusion regarding the direction of causality. Second, the analysis did not take into account schools as cluster units. Third, we did not adjust ORs for all the items that may be related to IA. For example, we did not ask questions regarding other psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD), which has been reported to be associated with IA [60‐62] and sleep disturbance [62] in adolescents. In this study, all participants attended daytime high school daily. In this setting, the number of students with ADHD is likely to be low. Fourth, students who were absent from school on the day of the survey could not participate. Fifth, our survey population was limited to students in a single prefecture in Japan; thus, it was a geographically limited population, so the results may lack generalizability. Finally, we did not investigate specific Internet-use disorders [4, 63‐69], which need to be studied in detail for preventive measures to be developed.

In summary, we observed that high Internet dependence was related to sleep disturbance in high school students in a prefecture in Japan. Studies have suggested that sleep disturbance and IA affect the gray matter in the brain. Longitudinal studies are required to further investigate the causal factors for IA and sleep disturbance and to clarify the mechanisms of their interdependence.