Intellectual Functioning and Severity of Autism Symptomotolgy Over Time

Background: A diagnosis of autism has been found to be stable over time, but there is considerable variability in the clinical profile, both between individuals with a diagnosis of autism and within each individual's unique profile over time. Because of this variability it is difficult to predict the course of autism and its distinctive expression in each individual with autism.

Objectives: The aim of the present research is to investigate the course of autism by following the changes in behavioral symptomatology, intellectual functioning and the association between them to examine the stability of diagnosis in early childhood.

Methods: Twenty-four children with autism were evaluated at two time points, the first at an average age of 4 years and 3 months and the second at an average age of 6 years. The severity of behavioral expressions of autism was evaluated using the Childhood Autism Rating Scale (CARS). Intellectual functioning was evaluated using the MSEL or the WPPSI, depending on age and level of functioning.

Results: Results revealed that the "severity of autism" was found to be stable over the period studied. In children below the average age of the sample and in children with IQ lower than 70 at initial assessment, there was an increase in severity of expression of autism symptomotology. Intellectual functioning remained stable over time, alongside changes in individual scores between the two examinations. A significant correlation emerged between behavioral expressions of autism and intellectual functioning over time. Furthermore, each variable at the first point in time was significantly correlated with the second variable at the second point in time. In other words, the more severe the behavioral manifestations of autism, the less change in IQ was observed over the period in question, and vice versa.

Conclusions: These findings provide a downward extension of previous research which studied stability of autistic features and intellectual functioning in older individuals with autism and support findings which report relative stability in the diagnosis of autism. The findings revealed that the period of early childhood in children with autism is also characterized by relative stability, of most behavioral expressions associated with autism and of intellectual functioning. Initial IQ measurement was found to be consistently and significantly associated with the changes observed over time, and with the power of the correlation between intellectual functioning and behavioral manifestations. It emerged from these results that while we may anticipate some degree of decline in intellectual functioning among children with initial IQ below 70, among those with initial IQ of 70 or above, we may anticipate stability of behavioral expressions and a modest improvement in general and performance intellectual functioning. Practically speaking, the results of this research may provide professionals who work with young children with autism a broader perspective on the disorder and a better ability to anticipate its course and its variability over time. These factors may be taken into account both in decision making and prioritizing intervention with individuals, and in educational placements.