Boer, M., van den Eijnden, R. J. J. M., Boniel-Nissim, M., Wong, S. L., Inchley, J. C., Badura, P., Craig, W. M., Gobina, I., Kleszczewska, D., Klanek, H. J., & Stevens, G. W. J. M. (2020). Adolescents' Intense and Problematic Social Media Use and Their Well-Being in 29 Countries.Journal of Adolescent Health, 66(6S), S89-S99.https://doi.org/10.1016/j.jadohealth.2020.02.014

1 - how were the adolescents recruited/selected?

2 - Does it give other demographic(e.g., gender)?