Efficacy and acceptability of cognitive behavioural therapy for insomnia in adolescents with insomnia and co-morbid mental health conditions: a systematic review; and Brief behavioural treatment for insomnia as a waiting list intervention for adolescents with insomnia and co-occurring mental health difficulties: a single-case experimental design study

Insomnia is common in adolescents and frequently co-occurs with mental health difficulties such as anxiety and depression. Converging evidence suggests a complex, bidirectional relationship between sleep and mental health. Insomnia is a risk factor for subsequent mental health difficulties and sleep problems. Sleep difficulties can aggravate the symptoms of the co-occurring mental health difficulty, and sleep problems can persist following the treatment of the co-occurring difficulty. Cognitive behavioural therapy for insomnia (CBT-I) is the recommended first-line treatment for insomnia. Most trials of CBT-I in adolescents have excluded those with clinically significant mental health difficulties. This thesis portfolio examines the psychological treatment of insomnia in adolescents with co-occurring mental health difficulties. Chapter one presents a systematic review of the efficacy and acceptability of CBT-I in adolescents with insomnia and co-morbid mental health conditions. Ten studies met the inclusion criteria, comprising both controlled and uncontrolled study designs in a variety of clinical settings. CBT-I was consistently associated with large improvements in self-reported insomnia severity and medium-to-large improvements in sleep onset latency and sleep efficiency, and no effect on total sleep time. Early indications of benefit were found for depressive symptoms. Acceptability was generally positive, although completion rates were variable. Certainty of evidence was very low across outcomes, reflecting a small and heterogeneous evidence base. Chapter 2 reports on a single-case experimental design study evaluating brief behavioural treatment for insomnia (BBT-I), a four-session intervention focused on the behavioural elements of CBT-I. The intervention was adapted and offered to adolescents with insomnia while on the waiting list for anxiety or depression treatment in a specialist outpatient mental health service. Three participants completed the intervention. Sleep onset latency improved for all three participants with large and statistically significant effect sizes. Total sleep time showed no change, and sleep efficiency improved for two participants. One participant showed near-perfect adherence to the prescribed rise-time. Her insomnia severity fell to a non-clinical level, and she showed a reliable and clinically significant reduction in psychological distress at 1-month follow-up. Uptake and retention were low, highlighting barriers to engagement. Together, this portfolio suggests that treating insomnia in adolescents with co-occurring mental health difficulties is feasible, safe and associated with meaningful improvements in sleep, particularly sleep onset latency, with preliminary indications of benefit for mental health. The findings support the routine identification and treatment of insomnia in adolescent mental health services, while underscoring the need for adequately powered trials and a better understanding of the factors that support engagement and adherence.