Dear Hassan, the review results of Cairns et al. (2014) were:
"Putative risk factors implicated in the development of depression for which there is a sound evidence base, and which are potentially modifiable during adolescence without professional intervention, are: substance use (alcohol, tobacco, cannabis, other illicit drugs, and polydrug use); dieting; negative coping strategies; and weight. Modifiable protective factors with a sound evidence base are healthy diet and sleep."
Cairns KE, Yap MB, Pilkington PD, Jorm AF. Risk and protective factors for depression that adolescents can modify: a systematic review and meta-analysis of longitudinal studies. J Affect Disord 2014;169:61-75. https://www.sciencedirect.com/science/article/pii/S0165032714004820
And there may be a link between internet addiction and depression among adolescents:
Lau JTF, Walden DL, Wu AMS, Cheng KM, Lau MCM, Mo PKH. Bidirectional predictions between Internet addiction and probable depression among Chinese adolescents. J Behav Addict 2018;7(3):633-643. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6426401/pdf/jba-07-03-87.pdf
Wu AM, Li J, Lau JT, Mo PK, Lau MM. Potential impact of internet addiction and protective psychosocial factors onto depression among Hong Kong Chinese adolescents - direct, mediation and moderation effects. Compr Psychiatry 2016;70:41-52. https://www.sciencedirect.com/science/article/abs/pii/S0010440X15303503?via%3Dihub
Cyberbulling, peer pressure to live up to the image portrayed on the teen’s social media page (Which is usually a rosier picture compared to real life), pressure to score well on exams to get into a “good” college, ineffective coping skills from a young age, influence of substances of abuse such as marijuana on the developing brain, unstable family life- many reasons