Attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD) are common childhood-onset neurodevelopmental disorders, which can co-occur. A diagnosis of ADHD and/or ASD typically gives rise to serious lifelong disabilities that cause considerable distress to individuals and their families. The transition from childhood to adulthood can be a particularly challenging time for young people with these disorders. These adults are more likely to experience a range of other behavioural and cognitive problems, yet these disorders go underdiagnosed in adults. This might reflect the presence of sub-threshold symptoms that do not meet the threshold for diagnosis but nevertheless are associated with cognitive impairment and/or mental health problems.The applicant's previous work in children who underwent comprehensive behavioural assessment has suggested that electroencephalographic (EEG) measures of executive and social function provide sensitive and objective markers that discriminate between ADHD and ASD and additionally help us understand the overlap between the disorders. However, it is currently unclear whether the cognitive impairments, symptoms of ADHD/ASD and associated emotional and adaptive functioning issues stem in part from a common cause, or rather co-occurring problems resulting from multiple causes. It is therefore of vital importance to conduct these investigations within a genetically sensitive design.To address this, we will collect data from two well-characterised twin sub-cohorts selected based on exhibiting high levels of ADHD and/or ASD symptoms in childhood. We will assess 300 twin pairs in person at ages 22-23 (200 twin pairs with at least one high-ADHD or high-ASD proband and 100 control pairs).Our proposed research has three objectives:(1) To investigate genetic and environmental origins of cognitive-neurophysiological biomarkers of ADHD and ASD and their overlap in young adulthood. Twin pairs will be assessed on executive function and social cognition tasks sensitive to ADHD and ASD symptoms. We will use innovative non-invasive mobile EEG technology to enable data collection in more familiar and natural settings, such as the home or workplace.(2) To characterise the persistence of symptoms and cognitive impairment into adulthood following a childhood diagnosis of ASD or ADHD. We will use longitudinal multivariate twin analyses to test hypotheses about development of symptoms in emerging adulthood, and further phenotypic analyses to investigate cognitive impairment even in those with sub-threshold symptoms.(3) To identify the overlap between adaptive functioning, mental health and neurophysiological function in young adults with ADHD and/or ASD. We will use the twin design to investigate the genetic and environmental origins of the overlap between symptoms, specific neurophysiological functions and mental health problems (anxiety and depression) and adaptive functioning.This will be the first study to address the aetiology of ADHD and ASD and their overlap in young adulthood using quantitative genetic and neurophysiological approaches. These data will provide information on the cognitive profiles, symptoms, mental health and adaptive functioning of people with ADHD and ASD during a critical developmental period for achieving life satisfaction and wellbeing. By using sensitive EEG measures that can be collected across abilities and environments, this project will provide the foundation for identifying objective neurobiological indices of these disorders and their outcomes in young adult life. We anticipate that this work will pave the way for identifying optimal treatment targets for these disorders and the design of more specific interventions to prevent emotional and mental health problems from developing. The innovative use of mobile EEG has the potential to transform neurophysiological research and routine clinical evaluation for psychiatric disorders.Technical SummaryAim: To investigate the aetiology and neurophysiology of ADHD and ASD and associated outcomes in young adulthood.Objectives:(1) To investigate genetic and environmental origins of cognitive-neurophysiological biomarkers of ADHD and ASD in emerging adulthood.(2) Document the aetiological influences and cognitive impairments associated with persistence of ADHD and ASD following high levels of symptoms in middle childhood.(3) To characterize the aetiological relationship between general functioning and mental health and neurophysiological function in young adults with ADHD and/or ASD. Methodology:The research will capitalise on two existing well-characterised sub-cohorts from the MRC-funded Twins Early Development Study (TEDS) that were enriched for ADHD and ASD symptoms in middle childhood (12-15 years). We will assess 300 twin pairs at ages 22-23 on a triad of measurements: (a) cognitive-neurophysiological assessments using EEG during tasks that the applicant and others have previous validated as sensitive to ADHD and ASD in childhood and adulthood; (b) in-person assessment using gold-standard diagnostic tools to obtain rates of ASD, ADHD and co-occurring ASD+ADHD in early adulthood; and (c) in-person interviews focused on mental health problems (anxiety and depression) and adaptive functioning.We will estimate genetic and environmental sources of variance and co-variance between neurophysiological impairment, ADHD and ASD symptoms and mental health/functional outcomes using the quantitative genetic MZ-DZ twin design. Additional longitudinal analyses will investigate influences on stability of ADHD/ASD diagnosis/symptoms and cognitive impairment outcomes.Scientific and clinical opportunities:This project could substantially advance understanding of ADHD and ASD in young adulthood, including risk for poor outcomes, ultimately to provide optimal targets for effective intervention and treatment.
Interagency Autism Coordinating Committee (IACC)
Autism Research Database (AFD)
