Despite the relationship between Autism spectrum disorder (ASD) and personality disorders (PD) still being scarcely understood, recent investigations increased awareness about significant overlaps between some PD and autism spectrum conditions. In this framework, several studies suggested the presence of similarities between BPD and ASD symptoms and traits, based on the recent literature that increasingly reported increased comorbidity rates and significant symptomatologic overlaps between the two conditions. The aim of this review is to describe the available studies about the prevalence of the association between different forms of autism spectrum (full-fledged clinical conditions as well as subthreshold autistic traits) and BPD. Despite some controversial results and lack of homogeneity in the methods used for the diagnostic assessment, the reviewed literature highlighted how subjects with BPD reported higher scores on tests evaluating the presence of AT compared to a non-clinical population and hypothesized the presence of unrecognized ASD in some BPD patients or vice versa, while also describing a shared vulnerability towards traumatic events, and a greater risk of suicidality in BPD subjects with high autistic traits. However, the specific measure and nature of this association remain to be explored in more depth.

Alterations in sensory processing, a key component of autism spectrum disorder (ASD), have recently attracted increasing attention as they result in peculiar responses to sensory stimuli, possibly representing a risk factor for the development of somatic symptom disorder (SSD). Contextually, other features also associated with ASD, such as alexithymia, camouflaging and altered verbal, and non-verbal communication, have been suggested to represent risk factors for the occurrence and worsening of somatic symptomatology. The aim of this work was to review the available literature about the association between SSD and the autism spectrum. The results highlighted not only a higher prevalence of autistic features in patients suffering from SSD and a higher prevalence of reported somatic symptomatology in subjects with ASD but also how ASD subjects with co-occurrent somatic symptoms exhibit more severe autism-linked symptomatology. From the paper reviewed also emerged many shared features between the two conditions, such as alexithymia, altered sensitivity to sensory stimuli, cognitive inflexibility, intolerance of uncertainty, and an increased risk of experiencing stressful life events, which may provide an explanation for the correlation reported. Even though studies on the topic are still scant, the evidence reported suggests the importance of further assessing the correlation between the two disorders.

Objectives: Hikikomori is a condition characterized by extreme social withdrawal, functional impairment, and mental distress, which has gained increasing recognition worldwide. While it can be associated with comorbid psychiatric disorders, hikikomori shares similarities with autism spectrum, prompting investigations into their relationship. Given that hikikomori commonly manifests in early adulthood, this study aimed to explore the relationship between autistic features and hikikomori tendencies among university students. Methods: A total of 2037 university students were recruited via an online survey and assessed with the Adult Autism Subthreshold (AdAS) Spectrum and the Hikikomori Questionnaire (HQ-25). Participants were categorized into four groups: healthy controls (HCs), subjects with hikikomori tendencies (HKs), subjects with significant autistic traits (ATs), and subjects with both significant ATs and hikikomori tendencies (AT-HKs). Results: Results showed significant effects of both hikikomori presence and significant ATs on AdAS Spectrum and HQ-25 scores, while a significant effect of their interaction was detected on AdAS Spectrum scores. The AT-HK group consistently scored higher on both AdAS Spectrum and HQ-25 compared to other groups, with the AT and HK groups outperforming HCs in specific domains. HQ-25 Socialization and Isolation domains predicted higher AdAS Spectrum scores in hikikomori subjects, while various AdAS Spectrum domains served as predictors of HQ-25 scores in AT subjects. Conclusions: This study highlights a significant relationship between ATs and hikikomori tendencies in university students, suggesting that their comorbidity may represent a more severe phenotype, where each condition may exacerbate the other.