To be included studies had to have at least one group of patients receiving a psychological treatment with a behavioural or cognitive component, have a group protocol or be a case study of at least three people, had to be in adults and report treatment outcomes. The participants had to have at least one anxiety disorder, such as generalised anxiety disorder, agoraphobia (with or without panic disorder), post-traumatic stress disorder, obsessive-compulsive disorder, social anxiety disorder, or social phobia.
Around half of the included studies were in patients with post-traumatic stress disorder; the rest were in patients with general anxiety disorder, panic disorder/agoraphobia, or a mixed sample of various disorders (one study). Most treatments involved both cognitive and behavioural components, but none directly addressed sleep difficulties. Most studies used individual and group therapies; in one study, treatment was given via the Internet. Mean age ranged from 30.7 to 50.3 years (where reported). Sleep was measured by a single item from a broader measurement, questionnaires and diaries; the number of sleep outcomes measured per study ranged from one to seven; most studies measured sleep alone, insomnia or nightmares.
The authors did not report how many reviewers performed the study selection.