Associations between childhood somatic conditions and psychiatric diagnoses in autistic young adults: a retrospective, population-based cohort study in Sweden.

Abstract

Autistic people are at an increased risk of psychiatric and somatic health conditions in young adulthood, but the influence of childhood somatic conditions on adult psychiatric conditions has not been examined. This study aimed to investigate whether childhood somatic conditions are associated with adult psychiatric conditions in autistic young adults. This retrospective, longitudinal, population-based cohort study design used data from linking nationwide Swedish registers. From the Medical Birth Register, we identified all individuals born in Sweden between Jan 1, 1985, and Dec 31, 2004 who were residing in Sweden at age 16 years. Between Jan 1, 2001, and Dec 31, 2020, individuals were followed up from age 16 years until a psychiatric diagnosis, their 25th birthday, death, emigration, or the end of follow-up, whichever came first. Autism, psychiatric, and somatic diagnoses were obtained from the National Patient Register and Prescribed Drug Register. We extracted diagnoses of nine childhood somatic conditions (asthma, chronic pain, epilepsy, cardiovascular conditions, migraine, autoimmune conditions, infections, irritable bowel syndrome, and type 1 diabetes) before age 16 years as exposures and ten adult psychiatric conditions (anxiety, obsessive-compulsive, depressive, bipolar, psychotic, sleep, and substance use disorders, anorexia nervosa, other eating disorders, and self-harm) between ages 16 years and 24 years as outcomes. Associations between childhood somatic conditions and adult psychiatric conditions were estimated using Cox regression in autistic and non-autistic people, adjusted for birth year and sex, with additional stratified analyses by sex and co-occurring intellectual disability among autistic people. We involved people with lived experience in the study design and implementation. From nationwide registers, we identified 1 944 781 individuals born between 1985 and 2004 in Sweden, including 58 410 (3·0%) autistic people (21 758 [37·3%] females and 36 652 [62·7%] males), who were followed up from age 16 years for a mean of 7·1 years (SD 2·8). Of 58 410 autistic people, 32 828 (56·2%) had any childhood somatic condition and 29 793 (51·0%) had any adult psychiatric condition. Of 1 886 371 non-autistic people, 835 810 (44·3%) had any childhood somatic condition and 251 333 (13·3%) had any adult psychiatric condition. Autistic people with any childhood somatic condition had an increased risk of any adult psychiatric condition compared with autistic people without any childhood somatic condition (adjusted HR 1·14 [95% CI 1·11-1·17]). For non-autistic people with versus without any childhood somatic condition, the adjusted HR was 1·41 (1·40-1·43). In people with any childhood somatic condition, autistic people showed an increased risk of any adult psychiatric condition compared with non-autistic people (5·36 [5·27-5·45]). In those without any childhood somatic condition, autistic people also showed an increased risk compared with non-autistic people (6·65 [6·53-6·77]). Although childhood somatic conditions contribute to adult psychiatric conditions, autistic people show elevated psychiatric vulnerability regardless of childhood somatic condition status. The findings highlight the need for integrated somatic-psychiatric health care and suggest that risk in this group is likely shaped by a broader range of factors beyond childhood somatic conditions alone. MQ Mental Health Research.