Castellanos 2006.

Methods	Design: RCT Conducted by the team who developed the intervention: yes
Participants	Description: targeted Cut‐point for inclusion for indicated studies: N/A What risk was basis of inclusion for selected studies: scoring one standard deviation above the school mean on the negative thinking subscale of the Substance Use Risk Profile Scale (SURPS; Conrod 2002) Diagnostic interview to exclude those with current or previous depression: not undertaken. Those with current and/or past depression not excluded, however. Baseline severity of depression: BSI: 16.0 (unclear)   Mean age: 14.0 Age range: 13 to 16 Percentage male: 35.7% Setting: school   State what psychiatric diagnoses were excluded: exclusion criteria not specified Suicide risk excluded: exclusion criteria not specified Parents with history of schizophrenia/bipolar disorder excluded: exclusion criteria not specified   Country: UK
Interventions	Broad category: CBT (for further information on intervention components, see Table 3) Manualised: yes Online: no Name of programme: not specified Number of sessions: 2 sessions Length of sessions: 90 minutes Intensity (total number of hours): 3 hours Duration of treatment period: unclear Group size: 2 to 9 Delivered by: mental health experts Fidelity: not assessed Type of comparison: NT
Outcomes	Diagnosis: N/A Name of self‐report depression measure: BSI Name of clinician report depression measure: N/A Name of anxiety measure: N/A Name of general functioning measure: N/A Assessment points: post‐intervention
Notes	Author contacted for methodological detail: no Author contacted for treatment manual: yes (not provided) Author contacted for outcome data: yes (provided)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information specified
Allocation concealment (selection bias)	Unclear risk	No information specified
Blinding (performance bias and detection bias) Subjects	High risk	The nature of the trial suggests it is unlikely participants could have remained blind to the fact they were allocated to a no treatment control group. However, without access to the participant information sheets and PLS, level of blinding cannot be ascertained.
Blinding (performance bias and detection bias) Assessors	Unclear risk	All outcomes self‐reported. Assessor blinding therefore not applicable.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Proportion of participants with incomplete post‐intervention self‐reported depression scores: 36.89% Means and SDs used in meta‐analysis based on what data: unclear Intention‐to‐treat analyses: authors state they use LOCF method, however, the number of participants included in this analysis is unclear
Selective reporting (reporting bias)	High risk	Protocol not available. Numbers of participants included in analyses are unclear, however, and yet there is a high proportion of treatment drop‐outs.
Other bias	Unclear risk	Trial conducted by those who developed the intervention
Implementation integrity	Unclear risk	Implementation integrity assessed: unclear if assessed Implementation integrity adequate: N/A Implementation integrity reported: N/A