Depression in Autistic Adults: Rumination and Insistence on Sameness
Objectives: Firstly, we investigated whether levels of rumination are higher in autistic adults compared to typically developing adults using a non-clinical sample. Secondly, we investigated the contribution of IS to depression in a mixed community and clinical autistic population and the potential for rumination as a mediator of this relationship.
Methods: We recruited a community sample of autistic participants (n=34) and typically developing participants (n=35). Autistic participants all had a validated diagnosis from a health professional. We also recruited a sample of autistic participants with validated clinical diagnoses of autism and depression (n=66) from NHS clinics who were participating in a clinical trial of a depression treatment (ADEPT). For the current study participants completed self-report measures of repetitive behaviour (IS subscale of RBQ-2A), Rumination (subscale of RRQ) and Depression (PHQ-9).
Results: As predicted, Rumination scores were significantly higher in the community autism sample (M=3.94, SD=0.70) compared to the typically developing sample (M=3.1, SD=0.89), t(67)=4.51, p<.001. Further, the community autism sample also had higher significantly higher scores on the depression measure (M=11.7, SD=6.1) compared to the typically developing sample (M=3.9, SD=2.5), t(66)=6.9, p<.001). A mediation analysis using ordinary least squares path analysis which included all autistic participants (n=100) found that IS scores affected depression scores via an effect on rumination levels. There was a significant positive effect of IS on rumination (a=0.52, p<.001) and rumination had a significant effect on depression scores (b=2.37 p=.01). A bootstrap confidence interval was generated for the indirect effect and was above zero (0.22 – 2.48). IS scores did still affect depression scores when controlling for rumination (c’= 2.12, p<.05), but to a lesser extent than when rumination was not included in the model (c=3.35, p<.001) demonstrating partial mediation.
Conclusions: Depression and rumination scores are higher in autistic people compared to non-autistic people. Moreover, insistence on sameness, a core feature of the Repetitive Behaviours domain in Autism, contributes to depression by increasing levels of rumination. Thus, a tendency towards behavioural repetition contributes to repetitive thinking patterns with negative content which contributes in turn to elevated depression symptoms.