It has been three years since the COVID-19 outbreak in December 2019. As of January 1, 2023, there were over 656 million confirmed COVID-19 cases and over 6.6 million deaths globally (WHO, 2023). Many countries once adopted compulsory measures (e.g., quarantine, community control, business and school closures) during the COVID-19 pandemic. As the vaccination became widely available, many countries gradually lift those restrictions (Ioannidis, 2022). There are three phases of COVID-19 response in China: 1) nation-wide lockdown (January 1, 2020 to April 29, 2020); 2) routine infection prevention and control (April 30, 2020 to December 6, 2022); and 3) lifting of COVID-19 restrictions (after December 7, 2022).

Both COVID-19 pandemic (e.g., infection) and COVID-19 related measures (e.g., quarantine) had a tremendous impact on mental health of adolescent and youth students (Fico et al., 2023; Xu et al., 2021; Yuan et al., 2021). Evidence showed that during the first wave of the COVID-19 pandemic, the prevalence rates of insomnia symptoms (36.7 %) and insomnia disorder (17.4 %) were approximately twice as high as the rates during non-pandemic periods (Morin et al., 2021). An increase in both the duration of gaming and the level of gaming addiction was reported in adolescents during the COVID-19 pandemic (Kim and Lee, 2021; Zhu et al., 2021). Previous studies in China indicated that there was a higher prevalence of depression (Zhou et al., 2020b), anxiety (Zhou et al., 2020b), PTSD (Z. R. Ma et al., 2021), insomnia (Zhou et al., 2020a), and internet addiction (Li et al., 2021) among children and adolescents during and after the COVID-19 pandemic than that in non-pandemic periods.

Meanwhile, COVID-19 infection may also play a significant role in mental health problems among adolescents. Individuals with COVID-19 infection may have more severe mental health problems, which may be related to that more severe inflammation among COVID-19 survivors may lead to increased severity of depression (Mazza et al., 2020). Moreover, previous studies have indicated that individuals with pre-existing psychological problems may be more vulnerable to COVID-19 infection, potentially due to their unique healthcare needs and cognitive impairments (Alshammari and Alshammari, 2021).

Although evidence suggests the significant impact of COVID-19-related psychological stress and COVID-19 infection on the mental health problems of adolescents, few studies on mental health problems in adolescent and youth students have been conducted after the lifting of COVID-19 restrictions in China. Moreover, most previous studies had relatively small sample sizes (e.g., <15,000 cases), and sample students were from only one school or certain grade levels (Prowse et al., 2021; Schwartz et al., 2021; Villani et al., 2021).

After the lifting of COVID-19 restrictions in China, it was estimated that a large number of people had been infected (Liang et al., 2023). The risk of COVID-19 infection may increase sharply which may also cause mental health problems among people infected. Previous studies mainly focused on the impact of psychological stress or COVID-19 infection on mental health problems (e.g., depression and anxiety) among adolescent and youth students (Z.-R. Ma et al., 2021; Schwartz et al., 2021). However, few studies have been conducted on the impact of both psychological stress and COVID-19 infection per se on mental health problems among students. It is still unknown about the mutual impact of both psychological stress and COVID-19 infection per se on mental health problems of adolescent and youth students. Thus, the aim of this study with large sample size was to explore the mutual impact of psychological stress and COVID-19 infection on mental health problems among adolescent and youth students after the lifting of COVID-19 restrictions in Sichuan, China.