McCambridge 2011.
Methods |
Design: Cluster‐randomised trial Follow‐up: 3 and 12 months Attrition: 18% |
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Participants |
Mean age (years): 17.5 Sex: 53% male N participants: n = 416 Allocation: n = 206 intervention n = 210 control (12 colleges; allocation not reported) Setting: further education colleges; all students Country: UK |
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Interventions |
Programme type: motivational interviewing Set‐up: delivery during a lesson to group of students Key components: participants were encouraged to think through and discuss a series of hypothetical situations in which they might find it difficult to refuse offers of drugs they had not previously used. Reasons for not using specific substances, and how initiation of use might affect future plans were explored Duration: 1 h Control: alternative intervention |
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Outcomes | Outcomes: measures of use assessed over the past month; measures of risk and harm for hazardous drinking; Alcohol Use Disorder Identification Test | |
Funding and Declared Conflicts of Interest | Funded by Big Lottery. Authors declare no conflicts of interest | |
Notes | Results included in MA only for baseline drinkers (n = 103 intervention and n = 99 control) | |
Risk of bias | ||
Bias | Authors' judgement | Support for judgement |
Random sequence generation (selection bias) | Low risk | Computerised randomisation stratified allocation by college, so that equivalent numbers of groups recruited from any one college would be allocated to each study condition |
Allocation concealment (selection bias) | Low risk | Randomisation was undertaken by the local Clinical Trials Unit and decisions were communicated by telephone to researchers after recruitment and baseline data collection on an individual college basis to preserve allocation concealment |
Incomplete outcome data (attrition bias) All outcomes | Low risk | Low attrition (18%). Intention‐to‐treat analysis performed |
Selective reporting (reporting bias) | Low risk | All prespecified outcomes were reported |
Blinding of participants and personnel (performance bias) All outcomes | High risk | Not possible to blind participants to intervention. Insufficient information to make a judgement about blinding of therapists |
Blinding of outcome assessment (detection bias) All outcomes | High risk | The researcher involved in the administration of the follow‐up data collection at any college had not been involved in the delivery of interventions in that college, though was not always blind to study allocation |
Unit of Analysis issues | Unclear risk | Stratified allocation by college, so that equivalent numbers of groups recruited from any one college were allocated to each study condition. No evidence of baseline differences. Clustering accounted for in statistical analysis reported in paper. but individual level data only available for inclusion in MA. ICC not reported. Study removed as part of sensitivity analysis |