The information below I have found at Mayoclinic.Com/
the onset of epilepsy can often be traced to an accident, disease or medical trauma such as a stroke that injures your brain or deprives it of oxygen, often causing a small scar in your brain. In rare occasions, epilepsy may be caused by a tumor in your brain. However, in many cases there's no identifiable cause for the disease.
Epilepsy isn't a mental disease, although mental health can influence the control of seizures in epilepsy. Epilepsy doesn't cause psychiatric problems or mental retardation, but people with epilepsy may also be afflicted with those conditions.