Insistence On Sameness in Asperger Syndrome Is Related to Cortisol

Background: Asperger Syndrome (AS) is characterized in part by a dysfunctional ability to adapt to novel experiences and environments, clinically referred to as a ‘need for sameness’ or ‘resistance to change’. The hypothalamic-pituitary-adrenal (HPA) axis modulates our ability to react emotionally and physiologically to change which culminates in the release of cortisol. Whilst individuals with AS have a preserved diurnal decline in cortisol (a decline from morning to evening), the Cortisol Awakening Response (CAR: a two-fold increase in cortisol release in the first 30 minutes after awakening) is significantly attenuated. The ADI-R is widely regarded as the most comprehensive assessment for AS and has been found to consist of two factors: ‘social and communication behaviours’ and ‘restricted and repetitive behaviours (RRBs)’. Further factor analysis within RRBs has identified two separate RRB factors: Insistence-on-Sameness and repetitive-sensory-motor-actions. Unlike repetitive-sensory-motor-actions, behaviours associated with Insistence-on-Sameness have been found not to be sensitive to developmental level and may be specific to AS.

Objectives: To identify if diurnal cortisol variations, the CAR or diurnal decline, related to RRBs in AS. We specifically examined the relationship between the CAR and the Insistence-on-Sameness factor of the ADI-R as these are the two aspects of HPA functioning and RRBs that may be specific to AS.

Methods: Data from this sample of 24 males (ages ranged from 9 to 16, mean = 12.3 years, sd=2 years) with a clinical diagnosis of AS has previously identified an attenuated CAR in this AS group. This data was combined with an analysis of the RRB subscale of the ADI-R. The researcher was blind to the cortisol level data when rating for current (during the period of saliva sampling) RRB behaviour using the 4 point scale of the ADI-R (current behaviour). To index levels of perceived stress during the period of sampling, participants completed the self-report, 20-item, Daily Hassles Scale.

Results: There was a significant correlation between the CAR and Insistence-on-Sameness (r₂₄=-0.44, p=0.016). The correlation between the CAR and Insistence-on-Sameness remained significant when it was rerun as a partial correlation controlling for both age and hassles (r₂₀=-0.43, p=0.048). The CAR did not correlate with the RRB total (r₂₄=-0.18, ns) nor repetitive-sensory-motor-actions (r₂₄=0.05, ns), although Insistence-on-Sameness did significantly correlate with repetitive-sensory-motor-actions (r₂₄=0.70, p<0.001). The CAR also did not significantly correlate with age nor hassles. Diurnal decline did not significantly correlate with either Insistence-on-Sameness or repetitive-sensory-motor-actions. The mean for Insistence-on-Sameness was significantly higher than the mean for repetitive-sensory-motor-actions (1.99(0.53) vs.1.08(0.50), repeated measures t-test t₂₃=10.93, p<0.001).

Conclusions: Increased severity of Insistence-on-Sameness behaviour (assessed through the ADI-R) was associated with decreased HPA axis activation (assessed through the CAR). This is particularly salient as Insistence-on-Sameness is the factor within restricted and repetitive patterns of behaviour argued to be specific to AS and an impaired CAR is the specific aspect of the diurnal HPA axis pattern impaired in AS. This is pertinent as Insistence-on-Sameness was identified as significantly more severe than repetitive-sensory-motor-actions, highlighting the need to research Insistence-on-Sameness specifically within AS.