Stability of the ADI-R
16
Investigation of the specific factors associated with changes in symptom severity over time highlighted
several T1 variables that were associated with outcome at FU. Correlational analyses indicated that T1
communication skills, IQ and symptom severity were highly correlated with outcome at FU. At an
individual level, comparison of those children who no longer met ADI-R criteria for autism at FU to
those whose ADI-R classification remained stable indicated that early adaptive behaviour skills may
also be an important factor in predicting later symptom severity. Comparison of individuals who made
the most and least progress on the ADI-R between T1 and FU also indicated that language skills at pre-
school age are likely to be associated with outcome at elementary school age.
In summary the findings from the current study suggest that children who have better language skills,
less severe autism symptomatology and higher adaptive behaviour skills at the pre-school age are more
likely to show improvements in symptom severity at elementary school age. This is consistent with the
findings of several previous studies (Charman et al., 2005; Coplan & Jawad, 2005; Eaves & Ho, 2004;
McGovern & Sigman, 2005). Interestingly, it should be noted that in this sample, improvements in
symptom severity were not notably associated with increases in IQ. In fact, IQ scores generally
remained stable or decreased between T1 and FU. However, MA scores did show an increase between
T1 and FU and therefore the improvements in symptom severity could, in part, be accounted for by
general developmental progress. This might be especially the case for items included in the ADI-R
algorithm that measure early communicative developmental abilities (e.g. gestures, nodding etc).
Methodological limitations
Whilst few studies to date have systematically assessed long term change in such young children with a
wide range of intellectual disability, the present sample may consist of a greater proportion of children
functioning within the moderate to severe range of disability than would be representative of the wider