The study found that social interaction impairments, stereotyped behaviours and specific interests were more severe in the individuals with Asperger syndrome also fulfilling SzPD criteria, against the notion that social interaction skills are unimpaired in SzPD. The authors believe that substantial subgroup of people with autism spectrum disorder or PDD have clear "schizoid traits" and correspond largely to the "loners" in Lorna Wings classification The autism spectrum (Lancet 1997), described by Sula Wolff. The authors of the 2019 study hypothesised that it is extremely likely that historic cohorts of adults diagnosed with SzPD either also had childhood-onset autistic syndromes or were misdiagnosed. They stressed that further research to clarify overlap and distinctions between these two syndromes was strongly warranted, especially given that high-functioning autism spectrum disorders are now recognised in around 1% of the population. Low weight
A study which looked at the body mass index (BMI) of a sample of both male adolescents diagnosed with SzPD and those diagnosed with Asperger syndrome found that the BMI of all patients was significantly below normal. Clinical records indicated abnormal eating behaviour by some patients. Some patients would only eat when alone and refused to eat out. Restrictive diets and fears of disease were also found. It was suggested that the anhedonia of SzPD may also cover eating, leading schizoid individuals to not enjoy it. Alternatively, it was suggested that schizoid individuals may not feel hunger as strongly as others or not respond to it, a certain withdrawal "from themselves".
Some individuals with SzPD who are in treatment say "life passes them by" or they feel like living inside a shell; they see themselves as "missing the bus" and speak of observing life from a distance.Aaron Beck and his colleagues report that people with SzPD seem comfortable with their aloof lifestyle and consider themselves observers, rather than participants in the world around them. But they also mention that many of their schizoid patients recognize themselves as socially deviant (or even defective) when confronted with the different lives of ordinary people – especially when they read books or see movies focusing on relationships. Even when schizoid individuals may not long for closeness, they can become weary of being "on the outside, looking in". These feelings may lead to depression or depersonalization. If they do, schizoid people often experience feeling "like a robot" or "going through life in a dream".According to Guntrip, Klein and others, people with SzPD may possess a hidden sense of superiority and lack dependence on other peoples opinions. This is very different from the grandiosity seen in narcissistic personality disorder, which is described as "burdened with envy" and with a desire to destroy or put down others. Additionally, schizoids do not go out of their way to achieve social validation. : 60  Unlike the narcissist, the schizoid will often keep their creations private to avoid unwelcome attention or the feeling that their ideas and thoughts are being appropriated by the public.