Gross 1995.

Methods	Design: Randomised controlled trial Unit of randomisation: Individual family Follow‐up: 1 year Study dates: 1989 to 1994
Participants	Participants: Both parents (23 mothers; 23 fathers) of children who met criteria for behavioural difficulty, as defined by a score of > 125 on the Eyberg Child Behaviour Inventory Mean age of parents: Mothers 32 (SD 4.8) years, fathers 33 (SD 4.9) years; mean, SD, range for entire sample, intervention and control groups: NR Child age: 24 to 36 months (mean, SD: NR); 20 (83%) boys and 3 girls Ethnicity: Not reported Number randomised: 23 families (10 intervention (10 mothers + 10 fathers + 11 toddlers); 13 control (13 mothers + 13 fathers + 13 toddlers)) Country & setting: USA; single‐site; recruited from urban medical centre and community; delivery of intervention not reported Eligibility criteria: Child aged between 24 and 36 months; both parents willing to participate, complete series of questionnaires and observation sessions at preintervention, postintervention, and 3 months postintervention; and child meets criteria for behavioural difficulty
Interventions	Two conditions: Group‐based parent training (Parenting Training Intervention); no intervention Duration of intervention: 10 (2 hours) sessions over 10 weeks Therapist training: Master degree in psychiatric nursing and experience
Outcomes	Externalising problems: Eyberg Child Behaviour Inventory ‐ intensity, as completed by mother (father report data not added) Secondary outcomes: Parent‐child interaction as measured by the Dyadic Parent‐Child Interaction Coding System, observer‐rated observation of mother and child (data for father‐child observation were not added) Timing of outcomes: Outcomes reported for postintervention, 3‐month and 1‐year follow‐up Adverse events: None specified
Notes	Level of prevention: Secondary or tertiary Funding: the National Institute for Nursing Research (grant no. R29 NR02013)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The study reported that participants were randomly assigned, but no further details were reported for a judgement to be made. We requested clarification from study investigators, but no further information was available at the time this review was prepared
Allocation concealment (selection bias)	Unclear risk	Information reported insufficiently for a judgement to be made. We requested clarification from study investigators, but no further information was available at the time this review was prepared
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants: It would not have been possible to fully blind participants in this type of study (there is an obvious difference between receiving group training and receiving no intervention). Participants were notified of their group assignment once randomisation was completed Personnel: The design of the study meant that personnel delivering the intervention were aware which groups had been assigned to the different study conditions
Blinding of outcome assessment (detection bias) Independent observer reported outcomes	Low risk	Dyadic Parent‐Child Interaction Coding System was assessed by observers that were unaware of child group assignments
Blinding of outcome assessment (detection bias) Parent reported outcomes	High risk	Eyberg Child Behaviour Inventory and Toddle Temperament Scale were assessed by parents who were not blinded to intervention condition
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Study investigators reported that 12 children of intervention group participants completed the 1‐year follow‐up assessment. In their initial study, investigators reported a total of 11 child participants; at 1‐year follow‐up, they reported a total of 12 child participants
Selective reporting (reporting bias)	Low risk	The published report included all expected outcomes, including those that were prespecified
Other bias	Low risk	The study appeared to be free of other sources of bias