Twenty-one studies were included in the review (n=8,976): three studies (n=1,976) evaluated e-based delivery methods and 18 studies (n=7,000) evaluated provider-based methods. Fifteen studies were randomised controlled trials and six were non-randomised controlled trials. Twenty studies were rated fair quality and one was rated good quality. Completion rates ranged from 60% to 100%
E-based delivery methods: OR 2.2 (95% CI 1.9 to 2.7). Cohen's d = 0.50. The authors described this as being a moderate effect.
Provider-based delivery methods: OR 1.1 (95% CI 1.0 to 1.2). Cohen's d = 0.03. The authors described this as being little to no effect.
All studies: OR 1.4 (95% CI 1.2 to 1.5). Cohen's d = 0.18