Autism spectrum condition is a lifelong neurodevelopmental condition recognised by its heterogeneous phenotypic manifestations. This heterogeneity not only makes the condition challenging to diagnose but may also lead to misdiagnoses of psychiatric or medical disorders, which can decrease quality of life and wellbeing. Research has shown that psychiatric and medical conditions are highly comorbid with autism, but it is not known if this is due to autism per se (i.e., autism-related genetic mutations and autistic traits) or the effects of environmental risk factors or protective factors. Environmental risk factors (e.g., traumatic experiences, intimate partner violence, bullying, stressful life events) commonly contribute to poor mental and physical health in the general population, but there has been less investigation into their role among autistic individuals. It is also unknown whether protective factors in childhood and adolescence (e.g., positive relationships with parents, school enjoyment, social support) affect the association between autism and psychiatric or medical comorbidities in adolescence and adulthood. In addition to examining these association in the general population who have an autism diagnosis, we will also consider autistic traits (i.e., the broader autism phenotype; BAP) and traits of attention deficit hyperactivity disorder (ADHD), which is highly comorbid in the autistic community. As girls and women were historically neglected in neurodevelopmental research, we will also examine sex differences. The research could have clinical and policy implications for promoting health and wellbeing in the broad autism population, better recognition and earlier diagnosis, especially among girls, and the prevention/promotion of risky/protective environments.