Quite a few years back, I talked about the idea that a diagnosis of autism or autism spectrum disorder (ASD) is seemingly not protective of other conditions/labels appearing alongside in the context of post-traumatic stress disorder (PTSD) (see here). Described as an 'anxiety disorder', PTSD is a complicated condition typically encompassing several key features: experiencing one or more traumatic events (natural disaster, victim of crime, experiencing various forms of abuse, etc) and subsequent re-experiencing of said events (flashbacks, nightmares, anxiety, etc) significantly impacting on day-to-day life.
The paper by Haruvi-Lamdan and colleagues  provides some further, welcomed, research interest in the relationship between PTSD and autism in the context that a "potentially unique perception of traumatic events, particularly from the social sphere" might predispose those diagnosed with autism to be more vulnerable to PTSD than other groups.
I've titled this post 'minus the psychobabble' because, unfortunately, there is still a body of thinking out there that tries to explain concepts like PTSD in terms of schools of thought such as the psychoanalytical for example. I don't want to get into the nitty-gritty of whether your 'ego balances the id' or whatnot (and how one would actually evidence such concepts), but I do want to keep autism away from psychoanalysis. I say all that in the context that Haruvi-Lamdan et al note: "While autism and trauma were often linked in psychoanalytic theory..." but go on to provide some slightly more evidence-based discussions.
Three important points are made by the authors as to how PTSD (and trauma in general) might be linked to autism.
"First, autism spectrum disorder (ASD) may serve as a vulnerability marker for posttraumatic stress disorder (PTSD), specifically by increasing the risk for exposure to traumatic events." Although not easy to say, a diagnosis of autism or the presence of clinically-relevant autistic traits does seemingly put someone at far greater risk for experiencing various traumatic events . I speak of peer-reviewed research talking about being a victim of bullying in the context of autism (see here) for example; noting that bullying is not always 'just playground shenanigans'. I would also refer you to some other factors that don't make for great dinner-table conversation in the context of autism (see here). And if you think that such factors are typically present only in childhood, think again. This all on top of the more usual likelihood of experiencing trauma that we all face.
"Second, PTSD, once it has appeared, may exacerbate certain ASD symptoms, for example, through maladaptive coping strategies and reduced help-seeking." I'm not in total agreement with the idea of 'maladaptive coping strategies' in the context of autism because science/practice does not really know enough about coping strategies (and concepts such as resilience) either in general or in the specific context of autism. I don't doubt that individuals with and without autism might have their own way of 'coping' but there is no evidence of some 'one-size-fits-all' across the entire diagnosis or population. I do agree that there may be aspects of autism that can lead to 'reduced help-seeking' as per the issue of communication and/or language use for example, and also the strength of social circles, but that's about as far as we can reliably say at this point.
"Third, there may be shared underlying mechanisms for PTSD and ASD, including neurological abnormalities associated with both disorders, as well as cognitive and behavioral mechanisms, such as increased rumination, cognitive rigidity, avoidance, anger, and aggression." Again there are some quite sweeping generalisations included in the authors writings here - 'neurological abnormalities'? - but they do raise some important points. Rumination - a deep or considered thought about something - coupled to perseveration is something that I've covered before in the context of autism (see here). It boils down to a potential heightened risk of 'not letting go' of a topic and how, in the context of trauma and PTSD, this could be something over-represented in the context of autism or the presence of autistic traits. Added to other issues such as an intolerance of uncertainty (see here) and you can perhaps see how autism and PTSD might not necessarily be miles apart. I probably didn't need to say it but will anyway, anxiety in the context of autism seems to be both rife and in many cases, is absolutely disabling (see here).
Although there may be several inter-connecting variables that potentially unite autism and PTSD, I don't want to lose sight of the heterogeneity that is present alongside both labels. Even in the context of experiencing some truly awful acts, there are disparities in whether PTSD is diagnosed in the context of autism  similar to the not-autism population. Diagnosis of autism and/or clinically relevant autistic features are likely to be only part of the picture here. That being said, there does seem to be grounds for quite a bit more investigation in this area, and onward, whether screening for PTSD in the context of autism should be more widespread and also examination of how effective the intervention(s) currently in place for PTSD are in the context of autism + PTSD...
 Haruvi-Lamdan N. et al. PTSD and Autism Spectrum Disorder: Co-morbidity, Gaps in Research, and Potential Shared Mechanisms. Psychol Trauma. 2017 Jul 20.
 Roberts AL. et al. Association of autistic traits in adulthood with childhood abuse, interpersonal victimization, and posttraumatic stress. Child Abuse Negl. 2015 Jul;45:135-42.
 Brenner J. et al. Behavioral Symptoms of Reported Abuse in Children and Adolescents with Autism Spectrum Disorder in Inpatient Settings. J Autism Dev Disord. 2017 Jun 7.