Preemptive, parent-mediated support for the early neurodevelopment of infants with family history of autism and ADHD in Brazil: Protocol for a randomised controlled trial evaluating the efficacy of the iBASIS intervention

Background: Autism and attention-deficit/hyperactivity disorder (ADHD) are common neurodevelopmental conditions that share genetic and neurobiological mechanisms. Infants with a first-degree family member diagnosed with one of these conditions are more likely to meet diagnostic criteria for the same or the other condition later in childhood. From the first year of life, these infants may show difficulties in social communication, self-regulation and sensory processing, as well as altered dyadic interactions with their parents. Preemptive interventions that can support the early development of these infants and promote positive outcomes for them and their families are a high priority for the field. The parent-mediated iBASIS intervention has shown efficacy in enhancing early social-communication development in infants with family history of autism or early social-communication difficulties. However, iBASIS has not been evaluated in non-English-speaking, lower resource contexts, nor for infants with family history of ADHD.Objective: To evaluate the efficacy of the iBASIS intervention in supporting the early development of infants with family history of autism and ADHD in Brazil.Methods: This is a single-site, two parallel-group randomised controlled trial of the experimental intervention (10 sessions over five months of iBASIS) versus five months of care-as-usual plus psychoeducational information (CAU+). Brazilian infants aged 6-to-11 months with a parent or older sibling with autism or ADHD are eligible to take part, along with their primary caregiver. Randomisation to iBASIS and CAU+ is stratified by family history, infant age and sex. Target sample size is 200: 100 infants with family history of autism (~50 iBASIS/50 CAU+) and 100 infants with family history of ADHD (~50 iBASIS/50 CAU+). The primary outcome is the weighted raw score of the Social Domain of the Communication and Symbolic Behavior Scales Developmental Profile Behavior Sample (CSBS-DP-BS). Secondary outcomes include parent-infant interaction behaviour, broader aspects of infant development and mental health of the primary caregiver. Primary and secondary outcomes are assessed pre-intervention and at 6-month endpoint. Longer-term outcomes (executive function, autism and ADHD traits) are assessed at age 24 months. Primary analysis will estimate the treatment effect on the primary outcome at 6-month endpoint using intention-to-treat longitudinal analysis of covariance in the autism and ADHD family history subgroups separately. Discussion: Findings of this trial will be important for the planning and use of preemptive interventions for infants with elevated familial likelihood of autism and ADHD, particularly in low-income settings.