Overall, children with epilepsy have poorer concentration and mental processing and are less alert than age-matched controls. The relationship between cognitive functioning and epilepsy is complex, however, with widely differing degrees of intellectual impairment--ranging from minimal to severe and progressive--related to diverse types of epileptic seizures, syndromes, and etiological factors. Prolonged and frequently repeated seizures are typically associated with more severe effects on cognitive functioning, particularly if epilepsy is symptomatic, i.e., secondary to a demonstrable brain lesion. A combination of such factors may contribute to the mental deterioration seen in many children suffering from severe epilepsy.