Objectives: The main objectives of this study were to (a) model distinct developmental trajectories of internalizing and externalizing behaviours among preschool children with ASD; and (b) examine the covarying pattern over time of these behavioural problems.
Methods: The sample consisted of 343 newly-diagnosed preschool children (mean age: 38.29; SD = 8.66; 290 boys) with ASD participating in a longitudinal multi-site study. Following diagnosis, the children were assessed three times at 6-month intervals using the Child Behavior Checklist (CBCL 1.5-5; Achenbach & Rescorla, 2000).
Results: Wave-to-wave correlations were first computed to examine the stability of problem behaviour and the co-occurrence of symptoms over time. Results indicated high stability for internalizing (T1 and T2 r=.67; T1 and T3 r=.62) and externalizing behaviours (T1 and T2 r=.64; T1 and T3 r=.64) and a high degree of concurrent co-occurrence (T1 r=.67, T2 r=.66 and T3 r=.77) which increased over time (Fisher z-tests=2.36; T3 >T1 and T2). Next, because correlations can mask distinct developmental patterns of behaviour, CBCL internalizing and externalizing total scores were also examined using a semi-parametric, group-based approach (PROC TRAJ). For internalizing problem behaviours, two distinct developmental trajectories were identified: a “decreasing low” trajectory consisting of 82.2% of children, and a “high” trajectory comprising 17.8% of children. For externalizing problem behaviours, two distinct developmental trajectories were again identified: a “decreasing low” trajectory comprised of 68.3% of the children, and a “decreasing high” trajectory comprising 31.7% of the children. Joint trajectory analyses indicated that children following a “high” internalizing trajectory were almost invariably represented on the “decreasing high” externalizing trajectory (87%). Conversely, children on a “decreasing high” externalizing trajectory were equally represented on the “decreasing low” (52.5%) and “high” (47.5%) internalizing trajectories.
Conclusions: Findings from this study suggest that (a) there are distinct developmental patterns of internalizing and externalizing problems among children with ASD; and (b) high severity of internalizing symptoms tends to be accompanied by high severity of externalizing problems. There also exists a relatively “pure” sub-group of children with ASD with high externalizing problems but low internalizing problems. The extent to which these groups differ on other variables (e.g., language, level of impairment, etc.) will be examined, as will the association of certain family variables (e.g., parental stress) with the intercepts and slopes of these trajectories.
See more of: Session Submissions