Study	Reason for exclusion
Bielmann 1978	This was a complex study that looked at the effect of clonazepam as an adjunct to phenytoin and phenobarbital in patients with mental retardation. It was complicated, however, by the stratification of patients into those receiving and those not receiving an antipsychotic. Age ranges were also not provided
Bjornaes 2013	Not people with intellectual disability
Conry 2014	Not a RCT
Donati 2006	The participants did not have an intellectual disability
Espe‐Lillo 1992	This conference proceedings abstract appears to be an open‐label, follow‐up study from a double‐blind trial. Requested further information from the authors but no reply received
Gidal 2013	Not people with intellectual disability
Hagebeuk 2011	Participants were all under 12 years old
Hellings 2009	Comparing methods of transitioning between 2 types of AED
Hodoba 2013	Not a RCT
Luna 1989	This study was not randomised
Santos 2013	Not people with intellectual disability
Schlumberger 1994	This study was not randomised
Smith 1968	IQ level of participants is above our inclusion criteria
Tolbert 2014	Not a RCT
Turner 1970	Only 1 patient was aged 12 or above. In addition, only 6/18 patients had Lennox‐Gastaut syndrome

AED: antiepileptic drug
 RCT: randomised controlled trial