Intelligence May Moderate the Cognitive Profile of Patients with ASD

Abstract

Background: The intelligence of individuals with Autism Spectrum Disorder (ASD) varies considerably. The pattern of cognitive deficits associated with ASD may differ depending on intelligence. We aimed to study the absolute and relative severity of cognitive deficits in participants with ASD in relation to IQ.

Methods: A total of 274 children (M age = 12.1, 68.6% boys) participated: 30 ASD and 22 controls in the below average Intelligence Quotient (IQ) group (IQ<85), 57 ASD and 54 controls in the average IQ group (85<IQ<115) and 41 ASD and 70 controls in the above average IQ group (IQ>115). Matching for age, sex, Full Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ) and VIQ-PIQ difference was performed. Speed and accuracy of social cognition, executive functioning, visual pattern recognition and basic processing speed were examined per domain and as a composite score.

Results: The composite score revealed a trend significant IQ by ASD interaction (significant when excluding the average IQ group). In absolute terms, participants with below average IQs performed poorest (regardless of diagnosis). However, in relative terms, above average intelligent participants with ASD showed the most substantial cognitive problems (particularly for social cognition, visual pattern recognition and verbal working memory) since this group differed significantly from the IQ-matched control group (p < .001), whereas this was not the case for below-average intelligence participants with ASD (p = .57).

Conclusions: In relative terms, cognitive deficits appear somewhat more severe in individuals with ASD and above average IQs compared to the below average IQ patients with ASD. Even though high IQ ASD individuals enjoy a certain protection from their higher IQ, they clearly demonstrate cognitive impairments that may be targeted in clinical assessment and treatment. Conversely, even though in absolute terms ASD patients with below average IQs were clearly more impaired than ASD patients with average to above average IQs, the differences in cognitive functioning between participants with and without ASD on the lower end of the IQ spectrum were less pronounced. Clinically this may imply that cognitive assessment and training of cognitive skills in below average intelligent children with ASD may be a less fruitful endeavour. These findings tentatively suggest that intelligence may act as a moderator in the cognitive presentation of ASD, with qualitatively different cognitive processes affected in patients at the high and low end of the IQ spectrum.

Fig 1. The effect of ASD and IQ on the cognitive composite score.

Standardized z-score composed of the speed & accuracy measures of all task variables. Higher z-scores are indicative of better performance (faster performance and/or less errors).

Fig 2. The effect of ASD and IQ on social cognition (face recognition, identification of facial emotions, prosody).

Measures of speed are depicted. Please see S1 Fig for measures of accuracy.

Fig 3. The effect of ASD and IQ on executive functioning (motor inhibition, set shifting, verbal working memory, visual working memory).

Measures of speed are depicted for inhibition and set shifting. Please see S2 Fig for measures of accuracy.

Fig 4. The effect of ASD and IQ on visual pattern recognition and baseline speed.

Measures of speed are depicted. Please see S3 Fig for measures of accuracy (visual pattern recognition) and variability (baseline speed).