Background and aims: Problematic social media use (PSMU) is a concerning public health issue among adolescents. Existing literature has paid attention to the role of singular family risk on PSMU, but how cumulative family risks affect the trajectory of PSMU needs to be further explored. Methods: The current study employed a five-wave longitudinal design that lasted for three years (each time interval: 6, 6, 12, and 12 months) to reveal the longitudinal mechanism between cumulative family risks and the trajectory of PSMU, examining the mediating roles of escape and relationship motivations. This study investigated 1,973 adolescents (Mage 5 14.51, SDage 5 1.49; age range: 11.95-17.45 years old; 47.4% females; 40% middle school) from southern China at wave 1, and the final sample size was 882 at wave 5. Results: PSMU among Chinese adolescents presented with a stable tendency. In addition, cumulative family risks positively predicted the initial level (B 5 0.21, SE 5 0.02, p < 0.001) but not the slopes of PSMU. Moreover, escape motivation mediated the association between cumulative family risks and the trajectory of PSMU (Bintercept 5 0.10, SE 5 0.01, 95%CI 5 [0.076, 0.118]; Blinear slope 5
0.03, SE 5 0.01, 95%CI 5 [-0.040,
0.019]; Bquadratic slope 5 0.004, SE 5 0.001, 95%CI 5 [0.002, 0.006]). Conclusions: Findings suggest that adolescents who experience cumulative family risks may be more likely to develop PSMU, potentially via the drive to escape from real life. A favorable family environment may be conducive to mitigating adolescent escape motivation and PSMU.  Kulcsszavak: cumulative family risks, problematic social media use, escape motivation, relationship motivation, adolescents