Randomisation
Randomisation occurred following completion of the T0 assessment. Randomisation sequences were computer generated by an independent staff member who was not involved in study implementation, using random block sizes of 2 and 4. To support practical implementation and to ensure adequate numbers in the EASE group sessions, separate randomisation sequences were created for males, females, and sibling pairs. Siblings were randomised in a separate stratum in order to maintain equal numbers between groups, and because sibling pairs could have mixed genders. Group allocations (EASE or ETAU) were recorded on pieces of paper, which were folded and placed inside sealed, numbered, opaque envelopes. The numbered envelopes were opened in sequence by the research coordinator with the allocation assigned to the corresponding adolescent on registration lists (having completed baseline assessments).