This is the first study comparing ASD traits, which were evaluated with gold-standard measures (ADOS-2 and AQ tests), to EDI-3 scores and BMI, in a sample of young patients hospitalized for AN. The investigation of ASD traits in childhood with the employment of the AQ “past version” represents a second new addition to the literature on the subject. Along with the quantitative measurement, multidimensional clinical evaluation of the patient was always taken into account since our Centre specializes in the diagnosis and treatment of both ASD and AN.
Five patients, of the 23 assessed (22%), obtained scores in the ADOS-2 compatible with a diagnosis of ASD. On the whole, 12 patients out of 23 (52%) scored above clinical thresholds for ASD in at least one test (ADOS-2, AQ childhood and adolescence). Notably, the patients, whom we analysed for this study, were considered on account of the presence of autistic features. The rationale for this choice was to explore and confirm possible criteria to select AN patients to be screened for ASD in clinical practice.
Our findings on the prevalence of ASD symptoms investigated with ADOS-2 in patients with EDs are consistent with most of the previous research. Particularly, a recent systematic review found a 26.5% prevalence of ASD in patients with ED (Nickel et al., 2019). A meta-analysis addressing the prevalence of ASD symptomatology among patients with AN found a wide spectrum of results, ranging from 4 to 52% (Westwood and Tchanturia, 2017).
Our finding of 26% patients scoring above thresholds for ASD in the AQ adolescence version is also consistent with previous research. Specifically, the mean score obtained in our population (21.9) confirms the results reported by a previous systematic review (Westwood et al., 2016). We documented strong correlations between the two versions of the AQ test, namely, total scores, as well as 4 out of 6 pairs of subscales, showed significantly correlated results between the childhood and adolescence version of the test. This could indicate that ASD traits pre-existed the onset of the ED. In this regard, ADOS-2 and AQ-adolescence total scores and subtests showed no direct correlation with patients’ BMI. These findings suggest that autistic traits documented in adolescent patients with AN may not be due solely to the severity of their condition during clinical evaluation, which confirms and expands on existing evidence (Sedgewick et al., 2019).
Correlation measures between tests for ASD and indicators of EDs showed that scores obtained at specific EDI-3 subscales, particularly IPC, APC and GMPC, were significantly correlated with AQ and ADOS-2 scores: this could suggest an association between ED psychopathology as assessed with EDI-3 and ASD traits. Multiple linear regressions adjusted for age, BMI and OCD comorbidity confirmed these findings. These results corroborate and widen previous data (Dell’Osso et al., 2018) for they show correlations between subthreshold ASD symptoms and selected EDI-2 subscales. In particular, the authors found Interpersonal Distrust EDI-2 subtest to be significantly correlated with total scores obtained at the Adult Autism Subthreshold Spectrum and with the Non-verbal communication and Inflexibility and adherence to routine domains. However, the ADOS-2 schedule was not adopted in this study. More generally, these results corroborate several previous studies, showing difficulties in social interactions and low levels of social skills in patients with AN (Klump et al., 2000; Anckarsäter et al., 2011; Postorino et al., 2017).
The present study has a limited and non-homogeneous sample of patients with regard to gender, BMI, psychiatric drugs and interval of time passed from discharge to evaluation. The self-report and parent-report questionnaires employed in this study allowed us to include various perspectives in the evaluation of the patients; on clinical observation, however, some biased attitudes towards the tests were noted, both coming from patients and parents. Nonetheless, most patients and parents were observed to be objective and compliant, and the clinical perspective given by the ADOS-2 permitted a well-rounded investigation.
In conclusion our results, although consistent with previous studies, are unprecedented in literature and should be investigated in larger samples, given their likely importance for both clinical practice and research. They indicate the possibility that the EDI-3 -- specifically its subscales IPC, APC, and GMPC -- be employed as a preliminary measure to identify and examine patients with AN for ASD traits with gold-standard measures.