. Author manuscript; available in PMC: 2017 Oct 11.

Published in final edited form as: J Pediatr. 2016 Jul 6;176:167–172.e1. doi: 10.1016/j.jpeds.2016.05.067

Table 1. Demographics of samples.

	Training set n=332 participants	Testing set 1 n=283 participants	Supplementary testing set n=464 participants
Age Mean(SD)	19.2 years (1.6)	21.4 years (0.7)	14.3 years (1.8)
Gender N(%)	Female: 289 (87.1%)Male: 43 (12.9%)	Female: 161 (57.8%)Male: 122 (43.1%)	Female: 219 (47.2%)Male: 244 (52.6%)No response: 1
Race/Ethnicity N(%)	Caucasian: 272 (82%) Asian: 25 (7.6%) Hispanic: 11 (3.2%) African American/Black: 15 (4.5%) More than One: 9 (2.7%)	Caucasian: 211 (74.6%) Asian: 40 (14%) Hispanic: 6 (2.1%) African American/Black: 4 (1.4%) More than one: 20 (7.1%) Other: 2 (0.7%)	Born in Netherlands: 453 (97.6%) Born outside Netherlands: 8 (1.7%) No Response: 3 (0.6%)
PRIUSS score	Mean(SD): 15.7 (10.8) Median: 13 Range: 0-60	Mean(SD): 12.1 (9.7) Median: 10 Range: 0-49	Mean (SD): 13.5 (9.3) Median: 12 Range: 0-55
Prevalence of PIU measured by PRIUSS	59 (17.7%)	26 (9.1%)	54 (11.6%)

PIU: Problematic Internet Use, PRIUSS: Problematic and Risky Internet Use Screening Scale