While the exact cause remains unknown in a large percentage of epilepsy cases, in those where the cause can be identified, factors such as nerve irritants, congenital anomalies, birth trauma, head trauma, cerebrovascular disease, tumors, brain infections, and excessive alcohol consumption are implicated. Brain cells discharge due to excessive electrical activity, and this disruption in the brain's electrical function leads to the recurrent seizures characteristic of epilepsy.

Other causes that can lead to epilepsy include:

Dementia
Age
Head injuries and trauma
Neurological causes
Stroke and other vascular diseases
Brain tumor
Excessive alcohol and drug use
Genetic factors such as Down syndrome

These types of epilepsy are termed cryptogenic or idiopathic. Epilepsy seizures can begin at any point in life. However, the most common age ranges for the onset of epilepsy are before the age of 20, particularly within the first three years of life and near adolescence.