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Table 1 Summary of characteristics of articles

From: A scoping review of the problems and solutions associated with contamination in trials of complex interventions in mental health

Variable Level Number of articles
Type of article (n) Results of primary analysis of clinical trial 228 (97.4%)
Design / protocol of clinical trial 3 (1.3%)
Results of secondary analysis of clinical trial 3 (1.3%)
Year (n) 2000–2004 47 (20.0%)
2005–2009 85 (36.3%)
2010–2015 102 (43.6%)
Country of origin (n) USA 101 (43.2%)
UK 39 (16.7%)
Netherlands 19 (8.1%)
Canada 14 (6.0%)
Australia 11 (4.7%)
Other 50 (21.4%)
Target population (n) Adult patients 172 (73.5%)
Children / adolescent patients 45 (19.2%)
People at risk 5 (2.1%)
Workers 12 (5.1%)
Target condition (n) Depression 30 (28.6%)
Substance abuse 18 (17.1%)
Psychosis 14 (13.3%)
Neurodegeneration 13 (12.4%)
Anxiety 6 (5.7%)
Attention deficit hyperactivity disorder 5 (4.8%)
Others 19 (18.1%)
Intervention (n) Cognitive behavioural therapy / CBT skills 33 (14.1%)
Care management / interdisciplinary care 26 (11.1%)
Education 21 (9.0%)
Motivational interviewing / motivational enhancement therapy 19 (8.1%)
Other psychotherapy / counselling 16 (6.8%)
Assessment and feedback 8 (3.4%)
Parenting interventions 8 (3.4%)
Others 103 (44.0%)
Phase (n) Early (pilot and feasibility trials) 29 (12.4%)
Late 205 (87.6%)
Level of treatment allocation (n) Participant level 141 (60.3%)
Cluster level 93 (39.7%)
Sample size (median; IQR) Participant-level allocation 143 (84–261)
Cluster-level allocation 285 (158–579)
Cluster size in cRCTs (median; range)   10 (3–200)