Studies in adults diagnosed with primary or secondary insomnia, undiagnosed sleep problems or reported poor sleep quality were eligible for inclusion. At least one group had to receive a psychological treatment with a behavioural or cognitive component and the study had to report treatment outcomes. Studies that did not report anxiety data, did not provide sufficient data to calculate effect sizes or that reported non-quantitative data were excluded.
The included studies considered various behavioural, cognitive or psychological treatments (some included anxiety management strategies) that included relaxation, sleep hygiene education and cognitive therapy in participants with primary insomnia, secondary insomnia, other sleep difficulties and post-traumatic stress disorder. A wide variety of questionnaires was used to measure anxiety constructs. Anxiety constructs included anxiety, arousal, worry and stress. The number of treatment sessions varied from zero to 22. Total duration of therapy varied from 15 to 1,560 minutes, where reported. Treatment delivery varied from group to individual to remote; some studies used a manual and some did not. Some studies included controls; others were pre-post studies. Most studies did not address anxiety. Where reported, the mean age of participants ranged from 20.59 to 80.63 years. Some studies included participants with comorbidities that ranged from alcohol abuse to cancer.
The authors did not state how many reviewers performed study selection.