The New DSM-5 Impairment Criterion for Autism Spectrum Disorder in Toddlers and Young Preschoolers

Background:  

In DSM-5 impairment is defined following the International Classification of Functioning, Disability and Health (ICF), thus closely related to adaptive functioning, and is conceptualized as caused by the symptomatology of the disorder. Our knowledge of how the new impairment criterion in ASD could be applied for young children is limited.

Objectives:  

To examine the effect of DSM-5’s new impairment criterion on ASD frequency in young children diagnosed according to DSM-IV-TR (Autistic Disorder, PDD-NOS), and to analyze the influence of the ASD specifiers intellectual impairment, language impairment and symptom severity as well as age and gender on impairment status.

Methods:  

Children (N = 127, 20-47 months) included in the study had a DSM-IV-TR clinical consensus ASD diagnosis and were assessed using the ADOS and the ADI-R. The composite score of the Vineland Adaptive Behavior Scales served as an indicator of impairment and different impairment levels were examined: mild (cutoff: 1 SD below the mean), moderate (1 ½ SD) and severe (2 SDs). Intellectual impairment was defined as NVIQ <70, language impairment assessed by the ADI-R and symptom severity by the ADOS Comparison Scores.

Results:  

Children (N = 127, 20-47 months) included in the study had a DSM-IV-TR clinical consensus ASD diagnosis and were assessed using the ADOS and the ADI-R. The composite score of the Vineland Adaptive Behavior Scales served as an indicator of impairment and different impairment levels were examined: mild (cutoff: 1 SD below the mean), moderate (1 ½ SD) and severe (2 SDs). Intellectual impairment was defined as NVIQ <70, language impairment assessed by the ADI-R and symptom severity by the ADOS Comparison Scores.

Results

Applying the mild impairment level, 88% of ASD cases fulfilled the impairment criterion, while the proportions were 69% and 33% for the moderate and severe levels. Intellectual impairment was significantly associated with increased impairment risk applying the moderate (OR = 2.92, 95% CI: 1.05-8.12) and severe levels (OR = 8.82, 95% CI: 3.20-24.33). Applying the severe level, language impairment (OR = 7.10, 95% CI: 2.02-24.98) and being a girl (OR = 3.33, 95% CI: 1.04-10.63) were also significantly associated with increased impairment risk. Symptom severity (ADOS comparison scores) was not associated with impairment status for any cutoff.

Conclusions:  

Depending on the chosen VABS cut-off level, DSM-5’s new impairment criterion seems to imply that the criteria for ASD is more restrictive than previously for a substantial part of young children. Thus, a strict application of the new DSM-5 impairment criterion in ASD might compromise the possibility of (really) early ASD diagnosis. Intellectual impairment and language impairment tended to be most strongly associated with impairment. The link between symptomatology and impairment as well as the definition/operationalization of impairment in ASD needs more consideration. Impairment might be more closely associated psychopathology with growing age, while more subtle in young age.