Intervention durations were not specified, but follow-up durations lasted 1 to 6 months. The comparison groups primarily consisted of a waiting list or a no-treatment control.

CBT-I improved the following sleep outcomes (which were mostly assessed using subjective questionnaires):

Insomnia (large effect size, 6 studies)
sleep latency (large effect size, 6 studies)
sleep duration (medium effect size, 6 studies)
sleep efficiency (medium effect size, 5 studies).

The improvements in insomnia symptoms also remained in follow-up appointments (medium effect size, 5 studies).

The risk of bias was low in 4 studies, unclear in 3 studies, and high in 1 study.

Cognitive behavioral therapy for insomnia in adolescents Original paper