Developmental and environmental differences in infants with family history of autism and ADHD during the first year of life in Brazil.

Infants with family history (FH) of autism or attention-deficit/hyperactivity disorder (ADHD) are likely to experience a range of differences in their early development compared to infants without FH. However, the vast majority of evidence concerning the early development of these infants has come from high-income-country (HIC) contexts and has not considered the role of psychosocial environmental factors. In this study, we investigated developmental and environmental differences in a large cohort (N = 252) of infants aged 6-11 months (mean=8.7 months) with FH of autism (n = 36), ADHD (n = 66), autism and ADHD (n = 84) or without FH (n = 66) in a low-and-middle-income-country (LMIC) setting, Brazil. Infants with FH of autism showed significantly lower adaptive daily living skills as well as significantly lower temperamental perceptual sensitivity and vocal reactivity than infants without FH of autism, while infants with FH of ADHD showed significantly higher temperamental activity levels and significantly lower temperamental recovery from distress and cuddliness than infants without FH of ADHD. Compared to infants without FH, infants with FH of autism and/or FH of ADHD had significantly higher levels of caregiver mental health difficulties and household chaos. Our findings suggest partially non-overlapping profiles of developmental differences associated with FH of autism and FH of ADHD and shared environmental difficulties in the home. This work highlights the importance of providing support for infants with FH of autism and ADHD and their families in Brazil.