Electrophysiological correlates of psychopathology in individuals with mental retardation and epilepsy.

One hundred adults with mental retardation and epilepsy were randomly selected from hospital and community settings for a detailed study of psychopathology (maladaptive behaviour, psychiatric illness and personality disorder). All of them had a recording of interictal EEG within the 12-month study period. Of all the EEG recordings, nine were completely normal, 48 showed excessive slow background wave, and a further 43 showed epileptiform discharges. Of the 43 with epileptiform discharges in the EEG, 12 showed bilateral, diffuse, generalized activities (including 3 Hz abnormality), 18 showed temporal lobe focus (five left-sided, four right-sided and nine bilateral), and the other 13 showed secondary generalization from a temporal lobe focus. A comparison of psychopathology between the groups with a generalized epileptiform activity in the EEG (n = 12) and focal changes (n = 18) did not reveal any significant differences.