At first glance, IQ and epilepsy may seem to have no clinical relation whatsoever. Unlike the association between IQ and autism(ASD), which appears to manifest through cognitive, communication, and social impairments, the association between IQ and epilepsy is less evident. But according the results of a recent study, low IQ in children with ASD puts them at increased risk for epilepsy.
Emma W. Viscidi of the Department of Epidemiology of the Division of Biology and Medicine at Brown University in Rhode Island conducted a study comparing the IQs of children with autism to see if it could provide insight into which children were at risk for epilepsy. Using a sample of 5,815 children with ASD, Viscidi found that 12.5% had epilepsy. When she looked at adolescents between the ages of 13 and 17, the rate increased to 26%.
The study revealed that the children with epilepsy had lower IQs than those without and that language impairment, functional regression, and severity of symptoms were all common in those with comorbid ASD and epilepsy. “The association between epilepsy and the majority of these characteristics appears to be driven by the lower IQ of participants with epilepsy,” said Viscidi. In fact, the risk of epilepsy decreased by nearly 50% with every one point increase in IQ.
Interestingly, Viscidi did not find gender differences in epilepsy rates. Aside from IQ, the other strongest predictor of epilepsy was older age, with children over the age of 10 having 2.5-fold increased risk of developing epilepsy. Viscidi is unsure if this is due to the longer duration of ASD, and if the chronicity increases the vulnerability for epilepsy. Or, as has been suggested by other research, the neurological deficits responsible for ASD are also responsible for epilepsy, predisposing ASD children for epilepsy. Regardless of the exact reason for the comorbidity, this research clearly shows that IQ could be an indicator of epilepsy and that clinicians treating children with ASD should be aware of this association early on.
Viscidi, E.W., Triche, E.W., Pescosolido, M.F., McLean, R.L., Joseph, R.M., et al. (2013). Clinical characteristics of children with autism spectrum disorder and co-occurring epilepsy. PLoS ONE 8(7): e67797. doi:10.1371/journal.pone.0067797