“…To aid in understanding the association of internet addiction and NSSI, multinominal logistic regression analyses were used to estimate the adjusted odds ratios (aORs) and 95% CIs of internet addiction and possible internet addiction for participants engaged in less-frequent or more-frequent NSSI separately, and different covariates were adjusted in 3 models to examine the robustness of the associations. In model 1, we adjusted for demographic characteristics of participants, including provinces (Anhui, Guangdong, Heilongjiang, Hubei, and Yunnan), sex (male or female), age groups (11)(12)(13)(14)(15)(16)(17), and 18-20 years), grade (junior high school or senior high school), and ethnicity (Han or others). In model 2, we also adjusted for covariates of socioeconomic status and family environment, including family income (<$150, $150-850, or >$850/mo), which was divided according to local economic level and referred to in a previous study, 30 family structure (single parent/restructured family, grandparents' family, combined family, or core family/stem family), single-child family (yes or no), parents' educational level (college or above, senior high school/technical school, or junior high school or below), parenting styles (strict, pampered, neglect or frequently changing, or open-minded).…”