[Analysis of multimorbidity trends and influencing factors of internet addiction and depression symptoms among middle school students in Zhejiang Province].

<b>Objective:</b> To analyze the multimorbidity trends and influencing factors of internet addiction and depressive symptoms among middle school students in Zhejiang Province. <b>Methods:</b> From 2018 to 2023, a multistage stratified random cluster sampling method was used to select middle school students aged 12 to 18 in Zhejiang Province. Internet addiction and depression status were measured by the Internet Addiction Scale and the Center for Epidemiologic Studies Depression Scale. When both symptoms were present, it was defined as multimorbidity.The multivariate logistic regression model was used to analyze the influencing factors of multimorbidity among middle school students, and a trend <i>Chi</i>-square test was used to analyze the changing trends of internet addiction, depression and multimorbidity prevalence. <b>Results:</b> A total of 193 505 students were included in the study. From 2018 to 2023, the prevalence of multimorbidity of internet addiction and depressive symptoms among middle school students ranged from 2.7% to 3.5%. The prevalence of internet addiction ranged from 4.7% to 6.0%, while the prevalence of depressive symptoms ranged from 18.7% to 25.1%. Multivariate logistic regression showed that boarding students (<i>OR=</i>1.34<i>,</i> 95%<i>CI:</i> 1.26-1.42), low-frequency (<i>OR</i>=1.59, 95%<i>CI</i>: 1.46-1.73), and high-frequency sugary drink consumption (<i>OR</i>=3.91, 95%<i>CI:</i> 3.55-4.31) increased the risk of multimorbidity among middle school students. In contrast, higher frequencies of moderate-to-high-intensity exercise (medium: <i>OR</i>=0.54, 95%<i>CI</i>: 0.50-0.58; high: <i>OR</i>=0.49, 95%<i>CI</i>: 0.44-0.55) and sufficient sleep (<i>OR</i>=0.52, 95%<i>CI</i>: 0.49-0.56) were protective factors. From 2018 to 2023, there was no significant change in the trend of multimorbidity prevalence among middle school students (<i>χ²</i>_trend=3.82, <i>P</i>=0.051). The prevalence of internet addiction showed an upward trend (<i>χ²</i>_trend=20.54, <i>P</i><0.001), while depressive symptoms showed a downward trend (<i>χ²</i>_trend=181.41, <i>P</i><0.001). <b>Conclusion:</b> The prevalence of internet addiction and depression symptoms among middle school students in Zhejiang Province remains stable from 2018 to 2023. The prevalence of internet addiction shows an upward trend, while the prevalence of depression symptoms shows a downward trend. The risk of multimorbidity is related to students' boarding, consumption of sugary drinks, lack of exercise, and insufficient sleep.