Arnarson 2009.

Methods	Design: RCT Conducted by the team who developed the intervention: yes
Participants	Description: targeted Cut‐point for inclusion for indicated studies: 75th to 90th percentile on the CDI What risk was basis of inclusion for selected studies: 75th percentile or higher on the negative attribution style composite of the CSAQ Diagnostic interview to exclude those with current or previous depression: those with current depression excluded as well as those scoring above the 90th percentile of the CDI, and those with a past episode of a depressive disorder Baseline severity of depression: CDI: 14.9 (mild‐moderate)   Mean age: not specified Age range: 14 to 15 Percentage male: 49.4% Setting: school   State what psychiatric diagnoses were excluded: dysthymia, cyclothymia, anorexia, bulimia, any psychotic disorder, bipolar disorder (types I or II), comorbid substance use/disorder, conduct disorder, oppositional defiance disorder and attention deficit hyperactivity disorder Suicide risk excluded: unclear Parents with history of schizophrenia/bipolar disorder excluded: unclear   Country: Iceland
Interventions	Broad category: CBT and IPT (for further information on intervention components, see Table 3) Manualised: yes Online: no Name of programme: not specified Number of sessions: 14 sessions Length of sessions: unclear. As sessions were delivered during usual class time, assumption is 1 hour. Intensity (total number of hours): 14 hours (on assumption each session has a duration of 1 hour) Duration of treatment period: 11 weeks Group size: 6 to 8 Delivered by: mental health experts Fidelity: not assessed Type of comparison: TAU comprising the ability to seek any school‐based or other services as necessary except those associated with systematic interventions
Outcomes	Diagnosis: Hodges' Child Assessment Scale, the A‐Life (for follow‐up interviews between 2003‐2005), or the K‐SADS (between 2004‐2005) Name of self‐report depression measure: CDI (data not reported in a usable format) 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, 12 months (medium‐term) for depression diagnosis only
Notes	Author contacted for methodological detail: yes (not provided) Author contacted for treatment manual: yes (not provided) Author contacted for outcome data: no Coding for depression severity at baseline: where baseline severity was mild to moderate as in this trial, it was rated as mild.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Participants...were randomly assigned..." (p.581) Method of randomisation not specified, however
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 an assessment only 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	Low risk	"All interviewers were uninformed as to the intervention condition of participants at all interviews" (p.580)
Incomplete outcome data (attrition bias) All outcomes	High risk	Proportion of participants with incomplete post‐intervention self‐reported depression scores: 12.87% Means and SDs used in meta‐analysis based on what data: observed cases Intention‐to‐treat analyses: not undertaken.
Selective reporting (reporting bias)	High risk	Scores on the CDI at follow‐up not reported
Other bias	High 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