In a recent meta-analysis, Eccles and Qualter  show that social cohesion is a strong factor in alleviating loneliness. Unlike Western cultures, which emphasize independence and individualism, Asian societies, including Indonesia, have evolved into a more socio-centric, collectivistic, and interdependent culture . This could explain the lower prevalence of loneliness among Indonesian adolescent girls and is reflected in the even lower rates found among adolescents with supportive parents and close and kind friends. The significant contribution of positive social relationships has also been consistently reported elsewhere [5, 6, 11], and our study shows that adolescent girls without close friends are 3.8 times more likely to experience loneliness.
Our study further shows the association between loneliness and several health-risk behaviors such as substance use (psychostimulants, drug use), psychosocial distress (being bullied, suicide planning and ideation, sleep disorders, no close friends), and a sedentary lifestyle. According to Peltzer and Pengpid , substance abuse is a way of coping with loneliness, and loneliness is a predictor of depression and suicide. Additionally, being bullied relates to the inability to form friendships [2, 29, 30]. Shaheen et al.  show that Jordanian adolescents that reported having reduced support from family or friends experienced more bullying. Kendrick et al. , on the other hand, found that the quality of one’s friends is protective against bullying. We found that adolescent girls bullied in the past month are 1.6 times more likely to experience loneliness than those who have never been bullied. While our study did not measure the association between social connectedness and bullying, the findings of the association between social disconnectedness, bullying, and the experience of loneliness indicate that this relationship might exist in our study sample. Nevertheless, loneliness is reported to be both a cause and a consequence of either being bullied [29, 30] or suicidal behavior [31,32,33]. The direction of association for either variable is unclear and would warrant additional investigation.
We also found associations between loneliness, as well as social and environmental factors such as hunger and passive smoking. The experience of hunger in this study is an indicator of the food insecurity situation and a proxy for the socioeconomic status of the study population. The finding that food insecurity may cause loneliness has also been found among Tanzanian adolescents [7, 34]. These authors link lower class socioeconomic status and limited family support to the likelihood of being hungry and also highlight the negative effect hunger has on mental health. A different study, even though in an older US population, shows that loneliness increases the likelihood of being hungry and recommends strengthening the social support system for this group . On the other hand, passive smoking is common, and smoking regulation in Indonesia is generally poor. The smokers, mostly males or fathers, smoke inside the home  and expose their lonely female adolescents who stay mostly at home. The increased odds of loneliness from passive smoking found in our study have also been consistent with previous reports, especially those using the WHO-GSHS data [6, 11]. However, the cause and effect of hunger, passive smoking and loneliness in adolescent populations is not well understood and requires further research.
The prevalence of loneliness among adolescent females may be lower in Indonesia but should still be a concern. Peltzer and Pengpid , in their study on loneliness in the general population of Indonesia, show that adolescents and the older population have the highest prevalence in the country. Considering the possible increased risk faced by female adolescents, national-level efforts should be age-specific and gendered.
This study’s limitations include that it was focused on adolescent females in schools because the GSHS is only conducted in those environments and, as such, findings do not represent all female adolescents in the country. The inclusion of female adolescents not attending school may generate different results. Additionally, the absence of covariates or use of loneliness as a single-item measure has been previously reported to be limiting as a qualitative indicator. The cross-sectional design also makes it difficult to measure causation. Future studies on loneliness may consider collecting primary data through longitudinal studies instead of using GSHS data.