Loneliness is a distressing feeling that arises when an individual’s social needs are not met by their social connections (Cacioppo et al., 2010). It has been associated with various physical and mental health issues, including depression, insomnia, and dementia (Groarke et al., 2021, McClelland et al., 2020, Sundström et al., 2020, Voitsidis et al., 2020). Moreover, lonely people face an increased risk of premature mortality (Holt-Lunstad et al., 2015). The prevalence of loneliness across different age groups is also concerning (Bao et al., 2021). A meta-analysis conducted across 113 countries, encompassing individuals aged 12 and above, revealed that a significant percentage (ranging from 1.8 % to 24.2 %) of the global population experience loneliness (Surkalim et al., 2022). This phenomenon is often referred to as the “loneliness epidemic” (Buecker et al., 2021, Lin, 2023).

Problematic Internet Use (PIU) is a public health issue that is frequently studied in relation to loneliness. PIU has adverse effects, including cyberbullying victimization, depressive symptoms, and suicidality (Ibrahim et al., 2022, Liu et al., 2023, Zsila et al., 2018). The prevalence rates of PIU vary across different countries, such as Italy (Vigna-Taglianti et al., 2017), Germany (Wartberg et al., 2020), China (Yang et al., 2020, Yang et al., 2020), Korea (Lee et al., 2018) and Southeast Asia (Balhara et al., 2018) range from 0.4 % to 47.4 %.

Although the association between loneliness and PIU has been extensively studied, there remains ongoing interest and debate regarding the temporal nature of their relationship and the variables that may affect the relationship. Considering the above-mentioned high prevalence and potentially severe psychological consequences associated with loneliness and PIU, it is crucial to understand the longitudinal loneliness-PIU relationship. Does loneliness lead people to PIU? Or does PIU lead to loneliness? Or do loneliness and PIU bidirectionally reinforce each other? Therefore, to expand our understanding of the longitudinal loneliness-PIU relationship, the present meta-analytic review quantitatively summarized the results of primary empirical studies. In addition, our review examined potential moderators that could explain the heterogeneity in longitudinal loneliness-PIU relationship.

PIU, a type of behavioral addiction, is a topic that is frequently studied in relation to loneliness. In recent decades, the number of people using the Internet, smartphones, and other electronic devices has dramatically increased (Meng et al., 2022). Although smart devices provide efficiency and convenience in various aspects of people’s daily lives, they also increase PIU, making it a significant public health issue (Lozano-Blasco et al., 2022). PIU is characterized by excessive or ineffectively managed urges and behaviors related to Internet use that cause subjective distress and/or interfere with essential life functions (Odacı and Çelik, 2013, Spada, 2014). The phenomenon was first conceptualized by Young (1996), and since then, it has garnered considerable attention. Despite the progressive changes in the ICD-11 draft and DSM-5 (Saunders, 2017), PIU still has a variety of subcategorizations, such as gaming addiction, social media addiction, pornography addiction (Block, 2008), internet addiction, and smartphone addiction (Kuss & Griffiths, 2011). In this study, PIU was used as a broad term to encompass these various forms of addiction.