Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Random assignment was accomplished by preparing a stack of sequentially numbered envelopes, and placing in each a card with a matching number and group assignment”.
Allocation concealment (selection bias)	Unclear risk	No description of allocation concealment was provided.
Blinding of participants and personnel (performance bias)	High risk	Blinding of participants and personnel was not possible due to the nature of the intervention and study design.
Blinding of outcome assessment (detection bias)	Unclear risk	No description of blinding of outcome assessment was provided.
Incomplete outcome data (attrition bias)	Unclear risk	Results are based on the data collected from the first 115 adolescents who completed the first quarterly follow‐up assessment of the 229 total recruited ‐ no significant difference from the overall pool of participants on any of the measures of psychological and social adjustment previously described (p<.10). Also, the exact number in each analysis varies from 104 to 115 due to missing data on some measures, there's no further explanation.
Selective reporting (reporting bias)	Low risk	No evidence of reporting outcomes selectively was detected.
Other bias	Low risk	No other potential biases were detected.