• autism spectrum disorder
• autistic traits
• biochemicals correlates
• social anxiety
• social anxiety disorder

Despite the ongoing research and the growing number of studies on the biological basis of many psychiatric disorders, data on anxiety disorders and specifically social anxiety (SAD) are still scant. Given the high prevalence of social anxiety in subjects on the autism spectrum, we aimed to investigate the biochemicals correlates of (SAD) among subjects with autism spectrum disorder (ASD), their first-degree relatives (BAP), and healthy controls (HCs). Blood samples were collected from all participants, and biochemical parameters were assessed using enzyme- linked immunosorbent assays (ELISA), all participants were also assessed with the Social-Phobia Spectrum – Self Report (SHY-SV). Results highlighted a higher prevalence of SAD in the ASD group, as well as higher scores at the SHY-SV and a greater tendency to use anxiolytics to improve social interaction skills. SAD subjects had significantly higher levels of homocysteine and inter leukin-6 (IL-6) and significantly lower levels of kynurenic acid and serotonin compared to non-SADs. IL-6 emerged as significant positive predictor of higher SHY-SR scores, while serotonin emerged as a negative predictor. Moreover, our results highlighted how specific parameters had predictive value over many SHY-SR domains. Overall, our results support the hypothesis of a role for the inflammatory cascade in the maintenance of SAD.