"Individuals with epilepsy are at increased risk of ASD [autism spectrum disorder], especially if epilepsy appears in childhood. Further, ASD is more common in the siblings and offspring of individuals with epilepsy, suggesting shared etiology."
That was the research bottom-line from Heléne Sundelin and colleagues  reporting results based on examination of the "Swedish Patient Register" with regards to the "risk of autism spectrum disorder (ASD) in individuals with epilepsy and in their first-degree relatives." Including one Jonas F. Ludvigsson, PhD on the authorship list (yes, he of 'gluten and autism: probably not coeliac disease but...' fame), researchers identified some 85,000 individuals diagnosed with epilepsy "as well as all their siblings (n = 80,511) and offspring (n = 98,534)." With some nifty statistical analysis including matching cases 5:1 with control participant data, they were able to conclude that around 1.6% of those with epilepsy were diagnosed with an ASD compared with 0.2% of controls. Those percentages are seemingly quite small both in real terms and also in differences between the groups but given the huge participant numbers included for study came out with a hazard ratio (HR) around 10.49 "confidence interval [CI] 9.55–11.53)." To put that HR of 10.49 in context, other work by Ludvigsson on epilepsy coinciding with coeliac disease for example, with a participant number in the tens of thousands came out with a HR of 1.42.
When also looking at what happened to siblings and offspring of those diagnosed with epilepsy, the authors also observed something of a potentially increased risk of autism being also diagnosed, although quite a bit less than risk to those themselves diagnosed with epilepsy. The results did however suggest that: "The risk in the offspring was particularly high in mothers with epilepsy." And just for good measure, the Sundelin results also noted that risk of epilepsy was "also associated with a prior diagnosis of ASD" confirming what many others have reported over the years (see here).
Although making some headlines I wasn't particularly shocked by the bi-directional associations reported by Sundelin and colleagues. Quite a few times on this blog I've talked about autistic features being potentially over-represented in cases of epilepsy (see here and see here) so to see some of those features crossing diagnostic thresholds into an actual autism diagnosis is perhaps not unsurprising. Continuing that line of thought I do wonder what might happen if the broader autism phenotype (BAP) was also analysed with epilepsy in mind (even the new DSM-5 categorisation of social communication disorder?)
Insofar as the hows and whys of the association between epilepsy and autism, well, we're still in guessing mode at the current time. I've talked about some of the various genetic syndromes that tend to include autism and epilepsy together as a diagnostic package (see here) as evidence for the more plural 'autisms'. Such syndromes suggest that mechanisms linking the two conditions are likely to be multiple and not necessarily the same for everyone. The issue of GABA and autism might also show some connection in some cases as per what is starting to be known about this neurotransmitter (see here) and where it might fit with some autism (see here) on top of epilepsy. Assuming also that epilepsy in pregnant mothers for example is being managed by medication, it is also not outside of the realms of possibility that certain preparations could also exert an effect on offspring autism risk (see here). I say this with no scaremongering intended.
I might also (speculatively) advance the idea that another research area might also be a connecting feature for some autism and some epilepsy: diet. Don't just click away yet as I will first bring your attention to the increasing peer-reviewed literature talking about the use of a ketogenic diet and autism (see here); said dietary intervention more typically indicated in 'some' cases of epilepsy. It's still early days but it strikes me that quite a bit more research is required in this area. Allied to the use of a ketogenic diet (see here) and also perhaps linking back to that other important research area frequently examined by Dr Ludvigsson (coeliac disease) I'm also inclined to ask whether some autism and some epilepsy might show a more specific connection to dietary gluten too. No, I'm not saying that a gluten-free diet nor a ketogenic diet is some sort of 'cure-all' for autism and epilepsy (please don't mess with epilepsy) but rather there may be overlapping genetics or biology potentially linked to facets of gluten metabolism that might be important for some on the autism spectrum with epilepsy. Certainly much more research on this and other less-traditional areas is indicated .
There are many questions that remain unanswered in this area of research. With regards to the here and now, well, the Sundelin and other data perhaps suggest that as and when epilepsy is diagnosed, preferential screening for autism could and should be offered particularly in infancy; and perhaps even offered family wide.
 Sundelin HEK. et al. Autism and epilepsy: A population-based nationwide cohort study. Neurology. 2016. June 15.
 Frye RE. et al. A review of traditional and novel treatments for seizures in autism spectrum disorder: findings from a systematic review and expert panel. Front Public Health. 2013 Sep 13;1:31.
Sundelin, H., Larsson, H., Lichtenstein, P., Almqvist, C., Hultman, C., Tomson, T., & Ludvigsson, J. (2016). Autism and epilepsy Neurology DOI: 10.1212/WNL.0000000000002836