Schizotypal Personality Traits in Autism Spectrum Disorders: What Are the Roles of Alexithymia and Anxiety?

Background: There is a large diagnostic overlap between autism spectrum disorders (ASD) and schizotypal personality disorder (SPD). In particular, characteristics associated with increased ASD traits have been linked with increased negative symptoms, social skills deficits, and disorganized behavior in SPD. In addition, the presence of anxiety can be identified in both ASD and SPD at high rates of prevalence. Alexithymia (a difficulty identifying internal emotional states) is often found among those suffering from anxiety in the general population and is associated with ASD and SPD traits. Furthermore, it is an influential moderator of the relationship between ASD traits and anxiety and is associated with anxiety in schizophrenia. Despite these suggested associations, the nature of this overlap is unknown but a better understanding of it could aid discrimination in differential diagnosis and inform intervention selection and design. While it has been shown that the overlap between ASD and SPD traits is not due to anxiety, it is possible that this overlap is explained not by anxiety per se but by alexithymia.

Objectives: We examined the relationship between ASD and SPD traits in adults with ASD, and the roles of alexithymia and anxiety in this relationship, using structural equation modeling (SEM).

Methods: A combined UK-US sample of 75 adults with a confirmed diagnosis of ASD completed self-report questionnaires. ASD traits were identified using the Autism Spectrum Quotient (AQ), SPD traits were identified using the Schizotypal Personality Questionnaire (SPQ), and alexithymia was assessed by means of the Toronto Alexithymia Scale—20 (TAS-20). Anxiety was a latent variable constructed using the Penn State Worry Questionnaire (PSWQ), the Trait form of the State Trait Anxiety Inventory—Form Y (STAI-T Form-Y), and the Fear of Negative Evaluation Scale—Brief (FNE Brief).

Results: The SEM analysis supported the hypothesis that alexithymia plays an important role in the relationship between ASD traits and SPD traits. All factor loadings were in the expected direction and there was converging evidence for excellent model fit. Simple relationships (ASD traits to SPD traits and ASD traits to anxiety) were significant when modeled individually but these were eliminated by adding alexithymia as a mediator (ASD traits to SPD traits; 89.4% of the influence) and reduced by adding SPD traits as a mediator (ASD traits to anxiety; 38.9% of the influence). In the combined model, ASD traits did not directly predict anxiety when controlling for alexithymia and SPD traits nor did they directly predict SPD traits. However, increased ASD traits did predict increased alexithymia and alexithymia predicted SPD traits. Increased SPD traits predicted increased anxiety but increased alexithymia did not.

Conclusions: Alexithymia and SPD traits both served as mediators for their respective relationships, albeit to differing degrees. These results suggest that the presence of SPD traits in individuals with ASD is largely explained by alexithymia symptoms and not the ASD traits themselves.