Randomised controlled trials, quasi-experimental trials and naturalistic comparisons were eligible for inclusion in the review if at least five participants were engaged in one-on-one online instant messaging or chat with a therapist. Studies needed to measure psychological symptoms, interpersonal and social functioning and/or quality of life. Studies that evaluated audio/video chat, web-based programmes and group-based interventions were excluded.
Included studies compared online chat against face-to-face counselling, telephone counselling or waiting list controls. The study populations included adults, children and undergraduate students. Most studies evaluated a single session of online chat; one evaluated a cognitive behavioural therapy-based intervention delivered over multiple sessions. Studies were conducted in Australia, Canada, England, the Netherlands and USA.
Two reviewers independently selected studies for inclusion. Any disagreements were resolved by consensus.