Experimental (randomised and non-randomised) and quasi-experimental studies of primarily web-based or web- and email-based interventions that targeted individuals older than nine years were eligible for inclusion. The authors needed to extract effect size statistics for behaviour change across health, safety, environmental and community development domains. Control groups had to contain print, web-based interventions, wait-lists, placebos or therapists.
A variety of participants were described (students, military personnel, diabetics, smokers, overweight individuals, church congregation), with a mean age of 34.7 years (range 15 to 62 years). Most were white and had a university degree. Many interventions were personalised and informed users about the consequences of their behaviour, helped set and achieve goals, encouraged skills learning, and provided feedback. Where reported, study adherence ranged from 21.2% to 100%; intervention adherence ranged from 26% to 100%.
The authors did not state how many reviewers selected the studies.