For infants and toddlers (roughly 0–3 years), the best-supported therapies are structured, developmental, and usually parent-mediated, rather than long blocks of clinic-based work with the child alone. Evidence is strongest for early social-communication interventions such as PACT,and naturalistic developmental behavioural interventions (NDBIs) summarised in Project AIM, while support for very intensive ABA or sensory-integration programmes in this age band is limited and low-certainty, as shown in the Cochrane EIBI review and the NIHR SenITA trial.
What do NICE, NHS England and WHO say about the early years?
NICE guidance for under-19s recommends that clinicians “consider a specific social-communication intervention for the core features of autism,” with parent-mediated approaches for pre-school children. NICE notes that small trials suggest early social-communication interventions can help, but it also stresses that there is insufficient evidence to recommend any one programme over another and calls for better early-years research.
NHS England goes further in its early integrated pathway (0–5 years), stating that there is “replicated evidence” that pre- and post-diagnostic PACT and the related video-based parent work can improve communication and reduce sensory sensitivities. It recommends offering evidence-based, developmental support as soon as developmental differences are noticed, not only after a formal diagnosis.
The World Health Organization (WHO) similarly states that timely access to early, evidence-based psychosocial interventions can improve communication and later participation in education, work and community life, while noting that most trial data come from pre-school samples and that evidence in infants is still emerging.
Parent-mediated therapies: What has the best evidence?
- PACT (around 2–4 years): A landmark trial and 5–6-year follow-up in pre-school children found that PACT improved parent–child communication and led to a moderate, sustained reduction in autism symptom severity into later childhood, though without clear effects on language or anxiety.
- IBasis-VIPP: (around 6–18 months): Trials in infants at high likelihood of autism suggest this video-feedback parent intervention can improve early social communication and reduce early autism-like symptoms, with some evidence of fewer children meeting full diagnostic criteria at age 3. This is promising but still based on relatively small samples.
- Other parent courses (e.g. Hanen “More Than Words”): These programmes help parents support communication through play, routines and follow the child’s lead. Trials show modest gains in parent strategies and some child communication measures, but overall evidence of quality is lower.
NDBIs, ESDM and other early developmental approaches
Naturalistic developmental behavioural interventions (NDBIs), including the Early Start Denver Model (ESDM), are usually started in toddlerhood (around 18–48 months). Meta-analyses such as Project AIM and its BMJ 2023 update find small-to-moderate improvements in social communication and early language, and more modest gains in adaptive behaviour. Most evidence is 2–5-year-olds, but it supports starting in the first years of life rather than waiting.
A 2024 JAMA Pediatrics meta-analysis also found no clear link between “more hours” and better outcomes, suggesting that quality, fit and family practicality matter more than simply maximising intensity.
What is limited or low-certainty evidence in 0–3s?
- Very intensive ABA/EIBI (20–40 hours per week): Reviews (including Cochrane EIBI review and NIHR how weak, low-certainty evidence mainly in slightly older pre-schoolers; there is very little robust data specifically in under-3s, and UK guidance does not recommend intensive ABA as standard early-years care.
- Sensory-integration therapy: Large UK trials in older children have not shown clear benefit over usual care, and there is almost no RCT evidence in infants or toddlers. Support at this age is usually framed as adapting to the environment rather than formal sensory-integration programmes.
Takeaway
For infants and toddlers with (or at high likelihood of) autism, the most evidence-supported options are structured, developmental, parent-mediated interventions that focus on early social communication and shared interaction, with NDBI-style approaches in toddlerhood. Claims that infants need very intensive ABA or sensory-integration therapy are not backed by strong UK or international evidence. Families are best supported by early, realistic, personalised help planned with their NHS team or local clinicians.
