Internet addiction among adolescents in Macau and mainland China: prevalence, demographics and quality of life

Internet addiction (IA) is common among adolescents and significantly determined by sociocultural and economic factors. The aim of this study was to compare the prevalence of IA among adolescents between Macau and mainland China and also examine its association with quality of life. A total of 2892 secondary school students were included. Standardized instruments were used to measure IA, depressive symptoms and quality of life. The overall prevalence of IA was 23.7%, with 32.5% in Macau and 19.8% in mainland China. Students in Macau were more likely to suffer from IA than those in mainland China (OR = 2.15, p < 0.001). Correlates of IA included being in higher school grades, poor academic performance, and more severe depressive symptoms. Students with IA reported lower quality of life in physical, psychological, social, and environmental domains. IA is common among Chinese adolescents, particularly in Macau. Considering the negative impact of IA on health and quality of life, regular screening and effective interventions should be undertaken for young Internet users.


Scientific RepoRtS
| (2020) 10:16222 | https://doi.org/10.1038/s41598-020-73023-1 www.nature.com/scientificreports/ Statistical analysis. Data analyses were performed using SPSS V24.0. Comparisons of socio-demographic and clinical variables between Macau and mainland China, and between IA and non-IA groups were conducted using independent samples t-tests, Mann-Whitney U tests, and chi-square tests, as appropriate. Normal distributions of continuous variables were checked by one-sample Kolmogorov-Smirnov test. Binary logistic regression analysis with the "enter" method was used to examine IA prevalence between Macau and mainland China, with IA as the dependent variable, study site (Macau vs. mainland China) as the only independent variable, after controlling for variables that significantly differed in univariate analyses. In addition, analysis of covariance (ANCOVA) was used to compare QOL between IA and non-IA groups after controlling for variables that significantly differed in univariate analyses. Binary logistic regression analysis with "enter" method was used to examine the independent correlates of IA. IA was the dependent variable, while those with significant group differences in the above univariate analyses were entered as independent variables. Significance was set at 0.05, with two-tailed tests.

Results
A total of 3380 students were invited to join this study, and 2892 agreed and completed the assessments: 882 in Macau, 500 in Beijing, 699 in Hefei, and 811 in Shenzhen. No significant differences in age and gender were observed between students who participated and those who refused to participate in this study. The basic demographic characteristics are shown in Table 1.
The overall prevalence of IA was 23.7% (95% CI: 22.1-25.2%), with 19.8% (95% CI: 18.0-21.5%) in mainland China and 32.5% (95% CI: 29.4-35.6%) in Macau (x 2 = 55.5, p < 0.001). There were significant differences between the Macau and mainland China in gender, being an only child, being senior secondary school students, living with family, self-perceived physical health and weight, academic performance and stress, relationships with classmates, teachers, and family, perception of family income status, parental educational level, parental work status and CESD score. No significant difference in IA prevalence between genders was found in mainland China (18.7% in boys vs. 20.5% in girls; x 2 = 1.02, p = 0.3) and Macau (33.3% in boys vs. 32.2% in girls; x 2 = 0.14, p = 0.71). After controlling for these variables, there were still significant differences between the two areas in IA prevalence (OR = 2.15, 95% CI: 1.68-2.74, p < 0.001).
The comparison of socio-demographic and clinical characteristics between the IA and non-IA groups is summarized in Table 2. Significant differences between the two groups were found in terms of age, study site, grade, self-perceived physical health and weight, academic performance and stress, relationships with classmates, teachers, and family, self-reported family income status, parental marital status and CESD score. After controlling for these variables, compared to the non-IA group, the IA group had a lower QOL in the physical (F = 4.5, p = 0.03), psychological (F = 6.2, p = 0.01), social (F = 7.1, p = 0.008) and environmental domains (F = 9.6, p = 0.002). Students in senior secondary school, with poor academic performance, and having more severe depressive symptoms were independently and significantly associated with higher risk of IA (Table 3).

Discussion
To the best of our knowledge, this was the first study to compare the prevalence of IA between adolescents in Macau and those in mainland China. IA is common in Chinese adolescents, particularly in Macau. Using the same IAT cutoff value, our findings were relatively higher than the figures reported in Western countries and other areas, for example, 5.8-12.1% in Italy 11,43 , 11.7% in Switzerland 44 and 7.9-18.2% in Turkey 10,45 . The prevalence in mainland China in this study was also higher than the corresponding figures among Chinese adolescents in previous studies, for example, 8.1% in eight cities in China 28 , 10.4% in Anhui province 46 and 12.2% in Guangdong province using the same IAT cutoff value 47 . The rapid growth of Internet use in China in recent years may contribute to the increased prevalence of IA in this study. According to the report from the CNNIC, the number of Internet users aged < 18 years was around 175 million in China, which accounted for 93.1% of this population 15 , with an annual growth rate of 3.7-8.1% 48 . In addition, widespread use of smartphones makes access to the Internet much easier than before. It was reported that 93.9% of Chinese adolescents accessed the Internet using their smartphones 15 . Furthermore, a rapid increase of online learning, entertainment and leisure activities made adolescents spend more time using the Internet 15 . All these factors are associated with increased prevalence of IA in China. It should be noted that no gender difference in IA prevalence was found in this study, indicating IA commonly occurs in both genders 49,50 . Students in Macau had a significantly higher IA prevalence than those in mainland China, which is similar to previous findings comparing IA prevalence between mainland China (17.1%) and Hong Kong (31.6%) using the same instrument 35 . IA is more prevalent in Macau than that in mainland China. Based on previous findings that IA was associated with high family income and socioeconomic status 28 , we speculated that higher IA prevalence in Macau is most likely due to economic and sociocultural reasons. Macau's per capita GDP ranks top five globally 30 , almost nine times higher than mainland China. Thus, with higher household income, adolescents in Macau may have access to electronic devices at an earlier age. A study found that 51.1% of adolescents had one personal computer in Hong Kong, while the corresponding figure was only 14.7% in mainland China 35 . This situation may be more widespread in Macau since the economic conditions in Macau are better still than in Hong Kong. Moreover, the wireless network infrastructures are well built in Macau, providing easy and free access to the Internet, and additional features (e.g., Facebook, and YouTube) of the internet are available in Macau, while these platforms are not widely available in mainland China. Additionally, as a former European colony, Macau is greatly affected by both Eastern and Western cultures, which may lead to different parenting styles regarding Internet use between Macau and mainland China 51 . Due to high degree of urbanization and good economic status, adolescents in Macau usually do not experience job-seeking pressures following graduation. Moreover, the living cost has rapidly increased in Macau in recent years, so adolescents' parents typically work, which results www.nature.com/scientificreports/ in decreased time to take care of their children. In contrast, their counterparts in mainland China face fierce competition in school, and they are highly occupied with homework, and therefore have limited time online with more strict parental monitoring 15,52 . All these factors likely contribute to the higher IA prevalence in Macau.
Higher school grades, poor academic performance and depressive symptoms were significantly associated with IA. Previous studies found that older adolescents were more likely to be addicted to the Internet 26,28 , which could be explained by several reasons. Compared to younger adolescents, older adolescents usually experience a more rapid phase of psychosocial, cognitive and intellectual development, and they start to take certain adult roles and consider long-term career goals. Thus, they often need to use Internet for information and social activities. Moreover, students in higher school grade are easier to access to the Internet 26,28 . Therefore, older adolescents are more likely to report higher IA rate. It may also be true that older adolescents are using their devices for online gaming, which is known to be highly addictive and increase in use around this age 53,54 .
The association between IA and poor academic performance found in this study supported earlier findings 27,55 . Studies found that "loss of control" moderates the association between IA and declining school performance 55 . Students suffering from IA usually spend a lot of time online, regardless of their school responsibilities. Some of them even skip class and sacrifice sleep time, resulting in fatigue and low degree of involvement in classes. The stress under the poor school performance may lead to further involvement of online activities for adolescents in order to escape negative emotions 56 .
Similar to previous studies 46,57 , we found the positive association between depressive symptoms and IA. Previous studies found that persons with IA usually lose rewarding experiences in their offline world and then feel socially isolated, which could increase the risk of depressive mood 20,58 ; in addition, those with depressive symptoms often use Internet to "self-medicate" as Internet use could alleviate depressive emotion 4,59 . The internet constructs a virtual and unrealistic world in which those with depression may obtain social support, self-identity, and the sense of achievement that cannot be satisfied in real world 16 . Nevertheless, excessive Internet use may impair daily functions and further worsen dysregulated mood. Some studies found a bidirectional association between depression and IA 60 .
Long-term Internet use and IA may cause physical problems, such as reduced physical activities and obesity 61 , physical pain (e.g., neck, shoulder and back pain) 62 , hearing impairment and impaired vision 63 , increased risk of accidents (e.g., falling, slipping, and bumps/collisions) 64 , disturbed circadian rhythm 65 , and poor sleep quality 2,65 . In addition, persons suffering from IA often have emotional and social problems, which may isolate themselves from peers, make them spend more time online and finally lead to additional adaption stress, and psychological and interpersonal relationship problems 3 . All these factors could cause lower QOL. As expected, IA was negatively associated with all QOL domains in this study, which is consisted with the findings of a meta-analysis 66 .
The strengths of this study included the large sample size, multisite design, random sampling, and the use of standardized instruments. Some limitations need to be noted. First, this was a cross-sectional study, therefore, the causal relationships between IA and a host of demographic and clinical variables are tentative. Second, due to logistical reasons, only three cities in mainland China were selected to represent the adolescents in central, eastern, and southern China. Therefore, the findings cannot be generalized to all parts of China, particularly rural areas. Third, the possibility of recall bias cannot be excluded. Fourth, the IAT only measures IA as a general construct, therefore, subtypes of IA were not measured in this study. In addition, there have been no standardized instruments on socioeconomic and cultural factors in China. Instead, a host of categorical variables, such as perception of family status, parental educational level, parental work status and marital status, were recorded as the index of socioeconomic status. Finally, some potentially confounding factors were not examined in this study, such as physical diseases and physical exercise.
In conclusion, IA is common in Chinese adolescents, especially in Macau. Given the negative impact of IA on health outcomes and quality of life, more attention should be paid to young Internet users, and regular screening and effective interventions should be undertaken for this population. Table 1. Socio-demographic and clinical characteristics of Chinese adolescents in Macau and mainland China. Bolded values are p < 0.05; academic performance: excellent = 85-100, good = 75-85, fair = 65-75, poor = < 65; Parental educational level: high = completion of at least undergraduate studies, medium = completion of secondary school studies, low = completion of primary school studies or not having completed any school study; Parental work status: unemployed = at least one parent is not employed, employed = both parents are employed; Parental marital status: married = complete original family with biological parents, others = remarriage, divorce, separation, or one or both parents passed away. CESD: Center for Epidemiologic Studies Depression Scale; IA: Internet addiction. a Chi-square test. b Mann-Whitney U test.