The clinical EEG and personality in mentally abnormal offenders

A retrospective survey was undertaken of the clinical EEG in a series of consecutive admissions to Broadmoor Special Hospital (N = 265). Following reporting of the records by visual inspection, the EEGs were classified according to 4 descriptive categories: predominantly monorhythmic; low voltage fast, 'choppy'; dysrhythmic with excess theta; and dysrhythmic with paroxysmal features. The last 3 categories constituted EEG patterns with atypical or anomalous features. The EEGs of patients with high scores on Welsh's MMPI Anxiety scale ('withdrawers') were compared with those of patients with low scores ('approachers'). Lateralization of paroxysmal EEG features was studied with reference to MMPI personality measures (Blackburn's Impulsivity and Sociability and Welsh's Anxiety), legal diagnosis, type of offence, and relationship to victim. The EEGs were studied in a further sample of 29 admissions who had been assessed, using Hare's Research Scale for the Assessment of Psychopathy (Hare, 1980). While the overall incidence of atypical EEG features reported in the present study (around 60% of cases) was comparable with that reported previously for offender populations, they occurred significantly more frequently in 'withdrawers' than in 'approachers'. This suggests that the high frequency of atypical EEG features in abnormal offenders may be due to the preponderance of 'withdrawers' in this population. Patients who had committed violent offences against strangers, as opposed to people known to them, tended to have bilateral paroxysmal features in their EEG. High scores on Hare's Psychopathy scale were significantly associated with prominent Posterior Temporal Slow Activity. The study offers some prospect that the combined use of EEG and personality assessments may be of potential value in the assessment of dangerousness.