Evidence from previous small trials has suggested the effectiveness of early social communication interventions for autism.

The Preschool Autism Communication Trial (PACT) investigated the efficacy of such an intervention in the largest psychosocial autism trial to date.

To provide a stringent test of a pre-school communication intervention for autism.

152 children with core autism aged 2 years - 4 years 11 months in a 3 site 2 arm single (assessor) blinded randomised controlled trial of the parent-mediated communication-focused intervention added to treatment as usual (TAU) against TAU alone. Primary outcome; severity of autism symptoms (modified social communication algorithm from Autism Diagnostic Observation Schedule-Generic, ADOS-G). Secondary outcomes; blinded measures of parent-child interaction, child language, and adaptation in school.

At 13 month endpoint the treatment resulted in strong improvement in parental synchronous response to child (adjusted between-group effect size 1.22 (95% CI 0.85, 1.59) and child initiations with parent (ES 0.41 (0.08, 0.74) but small effect on autism symptomatology (ADOS-G, ES -0.24 (95% CI -0.59, 0.11) ns). Parents (not blind to allocation) reported strong treatment effects on child language and social adaptation but effects on blinded research assessed language and school adaptation were small.

Addition of the PACT intervention showed clear benefit in improving parent-child dyadic social communication but no substantive benefit over TAU in modifying objectively rated autism symptoms. This attenuation on generalisation from ‘proximal’ intervention effects to wider symptom change in other contexts remains a significant challenge for autism treatment and measurement methodology.

Autism spectrum disorder (ASD) affects 20–30% of adults with intellectual disability. This group are vulnerable to challenging behaviour and mental health problems.

To explore the extent to which ASD affects challenging behaviour among specialist mental health service users with intellectual disability.

To identify predictors of challenging behaviour among adults who have intellectual disability.

A cross-sectional study of 92 participants from a specialist mental health service for adults with intellectual disability in the UK. The presence/absence of ASD was confirmed using the Autism Diagnostic Observation Schedule. Challenging behaviour was assessed using the Developmental Behaviour Checklist (DBC).

Participants with ASD (N=48) had higher total DBC scores than those without ASD (N=44; mean=54.2 vs. 29.2). ASD, severity of intellectual disability, age, presence of psychiatric disorder and total number of needs were entered as independent variables into a linear regression. The model accounted for 51% of the variance and was statistically significant (F(5,91)=18.1, p<0.001). Presence of ASD and total number of needs were the only significant predictors of challenging behaviour. Presence of ASD had the highest standardised coefficient (β=0.56).

Participants with ASD had significantly higher levels of challenging behaviour than those without ASD. Challenging behaviour was also independently associated with total number of needs. Understanding which service users with intellectual disability have higher levels of challenging behaviour than others despite receiving psychiatric treatment, and the extent to which having ASD is a contributing factor, should inform the development of more effective services and lead to improved outcomes.