Children and young people with autism spectrum disorders (ASD) are at very high risk of developing severe anxiety with associated behavioural problems that impair them in their everyday functioning. Amongst children without ASD family and environmental factors play an important role in determining which children develop anxiety and other mental health problems. However, much less is known about these factors in children with ASD. This PhD project will collect and use data from a longitudinal study of children with ASD to examine how family and other environmental factors contribute to severe anxiety and related problems in early adolescence. The QUEST follow-up study is as part of an NIHR programme grant. QUEST is a cohort of children who received an ASD r diagnosis in early childhood and were initially evaluated at 5-9 years of age. The present study involves two further waves of data collection (wave 2 and 3). Wave 2 (starting in 2014) focusses on child-specific, family-based and wider environmental risk and protective factors for mental health/behavioural problems. Wave 3 (2016+) will describe child outcomes with respect to severe mental health problems, other areas of functioning and quality of life. The PhD will focus on the role of family and wider environmental influences on the development and maintenance of anxiety and related problems. The student will participate in data collection and there is scope to contribute to selection of measures at wave 3. The student is encouraged to study the interplay between risk and protective factors and their application within a developmental biopsychosocial model. The student will learn a range of statistical techniques, including longitudinal analysis and growth curve modelling.The student will join a team within that programme, comprised of two researchers (post-doctoral and pre-doctoral) and another PhD student, and supported by an administrator.