It is well-known that children, young people and adults with neurodevelopmental disorders are more likely to experience mental ill health, and are often overlooked and underrepresented in research.^{Reference Hansen, Oerbeck, Skirbekk, Petrovski and Kristensen1–Reference Cooper, McLean, Guthrie, McConnachie, Mercer and Sullivan4} Clinicians working across all areas of health and social care are involved in providing services for people with neurodevelopmental disorders, and there is increasing focus upon ensuring they are knowledgeable about autism, intellectual disabilities and other neurodevelopmental disorders in order to help improve healthcare delivery. For us to help achieve this goal, we have brought together seven papers and three editorials that will be of interest to generalists as well as specialists already working with people with neurodevelopmental disabilities. It is notable that a number of papers are longitudinal cohort studies with large samples allowing researchers to investigate the relationships between a variety of developmental factors and outcomes over time. We highlight here the key points from the editorials and the papers.

Newbold & Busk (pp. 7–9) are both parent-carers who argue that it is important for practitioners and families and carers to work together effectively to help provide and shape care for children with neurodevelopmental disabilities. They argue that many of these challenges could be addressed by involving families directly in the commissioning of services using coproduction. Alexander et al (pp. 1–3) explore how the collaboration between health professionals, patients and family members can be made more meaningful in order to improve treatment outcomes and promote research. O'Grady & Hinshaw (pp. 4–6) focus on girls with attention-deficit hyperactivity disorder and report that they are at increased risk of abuse, maltreatment, self-harm and suicide. They argue that early diagnosis and intervention, before adolescence, is needed.

Baribeau et al. (pp. 20–27) report the findings of a longitudinal cohort study of children with autism in Canada. They developed a series of developmental trajectories for both anxiety and insistency on sameness from their data, noting that children who were considered to have ‘high-peaking’ insistence on sameness were more likely to develop clinically significant anxiety, whereas those with low insistence on sameness experienced fewer problems with anxiety. However, the relationship between insistence on sameness and anxiety over time was not consistent for all children; some children with less anxiety had greater insistence on sameness.

Henderson et al (pp. 58–62) examine the prescribing records of all children attending school in Scotland and report that those with intellectual disabilities were more likely to be prescribed antipsychotics and antidepressants compared with those without intellectual disabilities. The relative difference between the two groups of children fell over time, but this was because children without intellectual disabilities were more likely to be prescribed antipsychotics and antidepressants over time.

Du Rietz et al (pp. 35–42), using a large sample of sibling pairs from Sweden, examine the relationship between psychopathology, neurodevelopmental, externalising and internalising factors. They report that having controlled for general psychopathology, attention-deficit hyperactivity disorder was associated with neurodevelopmental factors, related to genetic effects, and associated with externalising factors, which were related to non-familial environmental effects, rather than genetics or the familial environment. The relationship between attention-deficit hyperactivity disorder and the internalising factor was explained by general psychopathology. The authors report that their findings suggest a genetic link between attention-deficit hyperactivity disorder and neurodevelopmental disorders.

Breda et al (pp. 43–50) report the findings from a longitudinal cohort study of children born in Brazil and followed up until they were 22 years of age to investigate and differentiate early- and late-onset attention-deficit hyperactivity disorder. Their findings support the view that the majority of those with attention-deficit hyperactivity disorder during young adulthood had a chronic and enduring trajectory, suggesting the disorder was associated with a neurodevelopmental pathway. However, there are a group who developed symptoms of attention-deficit hyperactivity disorder after pubertal onset who were predominantly women and those with higher general intellectual functioning.

Lin et al (pp. 51–57) made use of administrative data-sets in Ontario, Canada to investigate the probability of negative outcomes for adults with intellectual disabilities, relative to those without intellectual disabilities, both with and without a psychiatric diagnosis over time. They report those with intellectual disabilities had poorer outcomes relative to the general population without a psychiatric disorder, and this included an increased probability of readmission to hospital, delayed discharge and admission to a long-term care facility and premature mortality.

White et al (pp. 28–34) report the findings from two studies to help elucidate the relationship between the fragile-X premutation and the environment and the occurrence of autistic traits and anxiety among women. They report that mothers with the fragile-X permutation who have children with fragile-X syndrome are more likely to have autistic traits themselves in a similar way as to mothers of children with autism, and they are more likely to experience anxiety. These effects appear to have been associated with having the fragile-X permutation, rather than stress associated with having to care for children with neurodevelopmental disorders. The authors suggest that a fragile-X permutation phenotype should be recognised.

Rydzewska et al (pp. 10–19) is an umbrella systematic review, and the authors review the literature about physical health conditions among people with autism. They report that there is evidence that sleep problems, epilepsy, oral soft tissue injury, dental caries, incontinence and obesity are more common among people with autism. Gastrointestinal complaints appear to be more common among children with autism, but this was not consistent. Further, those who had hearing loss, visual impairment and atopy appeared more likely to have autism. Revealing these health inequalities, the authors argue that clinicians need an increased awareness of this comorbidity to help improve diagnosis and treatment.