Background Prior research has shown that chronic physical conditions in children are associated with a higher burden of mental illness. However, not much is known about the nature of this association among care-experienced children and young people in Scotland.

Methods The Children’s Health in Care in Scotland (CHiCS) is a population-wide study linking health and social care data for 13,830 care experienced children (CEC) and 649,771 general population children (GPC). Hospitalisations were followed from birth between 1990–2004 to the end of the study in 2016. Descriptive analyses were employed to compare differences in the prevalence of and hospitalisation rates (age standardised per 100,000 person-years) for mental ill health in the two cohorts, and between children with/without chronic physical conditions (epilepsy, asthma, and diabetes).

Results CEC were more likely to have mental health hospitalisations than GPC (5.1% and 0.8% respectively). Chronic physical conditions were associated with an increased risk of mental health hospitalisation, with, depending on condition, 7.18–9.38% CEC and 1.03–5.14% GPC hospitalised for mental health. The biggest impact was for GPC with epilepsy and diabetes. GPC with epilepsy had 6.4 times higher proportion of hospitalisations compared to those without epilepsy. The increase in mental health hospitalisations was driven by substance use, apart from GPC children with epilepsy, for whom disorders of psychological development was the primary contributor. Having a chronic physical condition increased the rate of mental health hospitalisation in both cohorts, but the effect was greater for GPC. The rate of mental health hospitalisations for children with chronic conditions was higher for CEC (rates per 100,000 for asthma = 1327, diabetes = 1415, and epilepsy = 2705 vs. 989 for no chronic condition) compared to GPC (207, 334, 922 as above vs. 126). For both GPC and CEC, epilepsy had the biggest effect on the rate of mental health hospitalisation, but this effect was more substantial for GPC.

Conclusion Children with chronic conditions are at an increased risk of mental health hospitalisations, which could have long-term consequences for their health, education and employment. The impact of chronic conditions on mental health hospitalisation is smaller among CEC, likely due to the already high prevalence of mental ill health in this cohort. Interventions to improve mental health would benefit from a specific focus on children with chronic conditions, especially among those with more serious illnesses, e.g. epilepsy.