Adolescence is a unique biological milieu and studies from adults cannot be generalised to adolescents. Depression typically has its onset during adolescent development. Studying a disorder at its onset presents an opportunity to understand the aetiology of a disorder. Complaints of disrupted (insomnia) or excessive (hypersomnia) sleep are common among adolescents with major depressive disorder (MDD). Previous studies have not addressed whether these two sleep subtypes in adolescent depression manifest different neurophysiology, clinical course or responsiveness to intervention. The current study will address these questions.
Sleeping Twins: The Genetics of Sleep and Cortical Development in Adolescence
Adolescence is a critical period in development, characterised by rapid biological, cognitive, emotional and social changes. Interacting with these processes, is sleep, which is also in flux during this period. Given the importance of sleep during this developmental period, the aim of this proposal is to unravel the genetic and environmental contributions to sleep, brain development, and cognition using a twin study. We will use two longitudinal assessments (six months apart) of sleep (sleep EEG) and brain structure (MRI) in 12-to-14-year-olds monozygotic and dizygotic twins to achieve the following specific aims: 1) Quantify the degree to which concurrent changes in brain structure, cognition, and sleep physiology observed during adolescence are due to common or unique genetic and environmental factors. 2) Quantify the heritability of sleep at two longitudinal time points six months apart. 3) Examine whether sleep duration in the intervening year between assessments shows high heritability and is predictive of the changes in sleep and brain structure/cognition. This proposal uses an integrative approach to elucidate genetic and environmental influences on sleep and brain development during adolescence.
Measures: Sleep EEG, MRI, MRS, Cognitive Function, Depressive Symptoms, Actigraphy