Case Series of Subclinical ASD: Evidence Towards the Female Protective Effect

Background: The sex ratio of males to females with ASD is 4:1. Females with ASD often have greater social communication weaknesses yet fewer restricted and repetitive behaviors than males (Rivet & Matson, 2011; Hartley & Sikora, 2009); however, recent evidence points to how current diagnostic criteria may miss females with ASD (Kirkovsk et al, 2013).

Objectives: We identified and characterized a subset of children who exhibited impairment in social functioning but did not reach the threshold necessary for an ASD. Their deficits were also not characterized by a different developmental or psychiatric disorder.

Methods: From a dataset of 1,626 children (793 females), ages 4-17, referred because of social communication deficits, 4 females and 1 male were identified who exhibited clear social and communication impairments, yet did not meet the threshold for a diagnosis of ASD based on criteria from gold standard diagnostic instruments and clinical judgment of highly expert clinicians. Social communication functioning was assessed using the Autism Diagnostic Observation Schedule (ADOS), Autism Diagnostic Interview, Revised (ADI-R), the Social Responsiveness Scale (SRS), the Social Communication Questionnaire (SCQ), and the Vineland Adaptive Behavior Scales-Second Edition (Vineland-II).

Results: Four females (.5%) and one male (.1%) from the overall dataset (N=1,626) presented with sub-threshold ASD symptoms. The females were between the ages of 6 and 12 years and of average to above average cognitive abilities (Full Scale IQ Range 92 to 118). The male was 9 years old and also exhibited average cognitive abilities (IQ = 97). The children had clear, yet either mild or inconsistent, social communication impairments. ADOS Total Scores (Module 3) ranged from 1-5, SRS T-Scores ranged from 53 to 90, and SCQ Total Scores ranged from 4-32, with a Total Score above 15 suggesting social impairments. Each individual had at least one measure within the range of clinical social communication impairment. Additionally, the children with completed Vineland Adaptive Behavior Scales (n =3) had highly significant impairments in adaptive functioning, with scores ranging from 61-68. Qualitatively, all of the parents reported noticeable difficulties with social verbalization, reciprocal conversation, and imaginative play due to limited flexibility.

Conclusions: A small but meaningful group of children exhibit sub-threshold ASD symptoms. This subclinical presentation is more common in girls than boys, despite the skewed sex ratio towards boys in ASD. These children with subclinical symptom presentation, particularly given the sex ratio, may provide information towards understanding the female protective effect.