The concept of autism has changed greatly over the past decades. One aspect of this has been a recognition that autism is rarely ‘pure’, and usually accompanied by other challenges, including intellectual and language disability, epilepsy, sleep and feeding difficulties, ADHD, and notably mental health conditions such as anxiety and depression. In this talk I will present research into mental health difficulties in autistic children and adults, with implications for families and schools. One factor in mental health is under-recognition of autism and late diagnosis; when autism isn’t recognised, appropriate understanding and adjustments are often absent, leading to more stress and worse wellbeing. This appears to be a particular problem for autistic females, who are typically diagnosed later than males, and many of whom may go undiagnosed. I will discuss possible reasons for under-recognition of autism in girls and women, and clinical and educational implications.