Joint associations of non-intact family types and health-risk behaviors with mental health outcomes: evidence from a large-scale survey among adolescents in Shandong Province, China

Rising global divorce rates have increased the prevalence of non-intact families, which may be associated with adolescents’ behaviors and mental health. Non-intact family types (NIFTs) and health-risk behaviors (HRBs) are both associated with adolescent mental health, yet previous studies have often examined these factors separately. Evidence remains limited regarding the clustering of HRBs, distinctions among specific single-parent and reconstituted family types, and the role of grandparent-headed families. This study examined HRB clustering among adolescents in Shandong Province and evaluated the independent and joint associations of five NIFTs and HRB classes with depressive, anxiety, and comorbid symptoms. From 2023 to 2024, a cross-sectional survey of 292,536 students from junior, senior, and vocational high schools across all 136 districts/counties in Shandong, China, was conducted using self-administered questionnaires on sociodemographic characteristics, 10 HRBs, and 5 non-intact family types. Latent class analysis identified HRB classes. Logistic regression was used to estimate the independent associations of family type and HRB classes, as well as the joint associations of their combined categories, with depressive, anxiety, and comorbid symptoms. Four HRB classes were identified, with the Unhealthy Diet class most prevalent (40.13%). Stepmother family had the highest odds of violent victimization experience and addictive behaviors (VVAB) (OR = 3.21,95%CI:2.39–4.31) and physical inactivity (OR = 1.89,95%CI:1.34–2.66), whereas stepfather family had the highest odds of unhealthy diet (OR = 2.40,95%CI:1.92–3.01). Only single-mother family showed higher odds of overweight (OR = 1.09,95%CI:1.03–1.15). The VVAB class had the highest odds of depressive (OR = 9.53,95%CI:9.12–9.97), anxiety (OR = 6.04,95%CI:5.84–6.24), and comorbid symptoms (OR = 10.18,95%CI:9.68–10.71). Stepmother family had the highest odds of anxiety symptoms (OR = 1.43,95%CI:1.22–1.68), whereas stepfather family had the highest odds of depressive (OR = 1.73,95%CI:1.51–1.97) and comorbid symptoms (OR = 1.75,95%CI:1.52–2.02). Among adolescents with VVAB living in stepfather family, the odds of depressive (OR = 21.10,95%CI:17.32–25.60), anxiety (OR = 9.94,95%CI:8.13–12.21), and comorbid symptoms (OR = 22.70,95%CI:18.50–27.80) were the highest. Non-intact families and clustered HRBs were jointly associated with depressive, anxiety, and comorbid symptoms among adolescents in Shandong Province. Adolescent health and mental health services may consider strengthening family relationships, addressing risky behaviors, and supporting mental well-being.