Alexithymic and autistic traits differentially predict personality disorder dimensions.

Alexithymia and autism are variably characterized by social cognitive and perceptual deficits, which can lead to profound social interaction difficulties. Such difficulties are also the hallmark of personality disorders (PDs), but the potential link between alexithymia, autism, and PDs remains unclear. Here, we investigated whether autistic and/or alexithymic traits are associated with specific PD dimensions as measured by the Assessment of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (-IV) Personality Disorders Questionnaire (ADP-IV). We included individuals with a formal autism diagnosis (AP,  = 89), individuals with a psychiatric diagnosis other than autism (NAP,  = 51), and neurotypical participants (NPs,  = 84). We applied linear regression analyses with autistic and alexithymic traits as predictors and PD dimensions as outcome variables, while controlling for age, depressive, and socially anxious symptoms. While autistic traits predicted the obsessive-compulsive PD dimension, alexithymic traits predicted the borderline PD dimension. Autistic and alexithymic traits were both significant predictors of the schizoid PD dimension. Taken together, our results point toward overlaps between autistic traits and specific PD dimensions that are well recognized as differential diagnoses of autism, while alexithymia was differentially linked to the borderline PD dimension.Lay abstractAutistic people have trouble identifying their own emotions and others' emotions. They also struggle to describe their emotions. People with alexithymia have similar difficulties. This can make it hard for autistic and alexithymic people to react appropriately to situations. Some may avoid places, while others may start overthinking. This can lead to patterns of behavior and thinking that limit us in our daily lives. If these patterns become a part of our personality, we may develop a personality disorder (PD). In our study, we looked at whether autistic and alexithymic people have certain PD dimensions. We included autistic participants, non-autistic participants with social-interactive difficulties, and non-autistic participants without social-interactive difficulties. We found that autistic features were linked to obsessive-compulsive PD dimension. Alexithymic features were linked to borderline PD dimension. Autistic and alexithymic features were linked to schizoid PD dimension. Our results point toward overlaps between autistic traits and PD dimensions that are well recognized as differential diagnoses of autism. The exception was borderline PD dimension, which was linked to alexithymic traits.