A large proportion of the population with intellectual disability (ID) have associated disabilities such as challenging behaviour, spastic quadriplegia, epilepsy, and vision and hearing impair- ment. 1–3 Such disabilities are found to predominate at more severe levels of ID, implicating more severe brain injury as being responsible for frequent complications. Epilepsy is the most frequent single disability seen in approximately 15–30% of cases of ID. 3 The general population prevalence estimate of epilepsy is 0.4%, 4 which suggests that there is an association between epilepsy and ID. There has also been a long established link between epilepsy and psychopathology, with as many as one-third to one-half of all adults in the general population with epilepsy estimated to also suffer from psychiatric disorder. 5 An association between ID and increased prevalence of psychopathology has also been well established in a number of studies. 2,6 Major recent advances in the treatment of epilepsy make it imperative to extend these advances to people with concurrent epilepsy and ID. Contemporary controlled studies have failed to demonstrate a clear link between psychopathology and epilepsy in individuals with ID. 7,8 However, these findings are in contrast to older studies which did not use matched controls and found evidence of a ‘double handicapping’ affect of epilepsy and ID. 9,10 In recognition of this, Espie et al. 11 identi- fied the need for further descriptive assessment of the specificity range and severity of behavioural and emotional problems asso- ciated with the dual disability of epilepsy and ID. The current study aims to advance our knowledge of how epilepsy, or certain features of epilepsy, may predict the presence of behaviour disturbance among a cohort of young people with ID. This study examined whether the additional handicap of epilepsy in young people with ID is associated with an increase in behavioural and emotional problems. Moreover, the characteristics of young people with both ID and epilepsy were examined to determine how such factors as age, sex, cognitive level, and control of epilepsy via medication influence emotional and behavioural problems in young people with ID. METHOD Subjects An epidemiological cohort of 392 participants who are repre- sentative of the general Australian population of young people with ID, aged 8–22 years, some of whom have symptoms of epilepsy, were used in the study. Full details of the sample are described elsewhere. 12 One hundred and fifteen individuals from this cohort were identified as suffering from epilepsy as reported by the primary carer. Criteria for classification included a history of seizures, J. Paediatr. Child Health (2000) 36, 172–175 Epilepsy and associated psychopathology in young people with intellectual disability JN LEWIS, 1 BJ TONGE, 1 DR MOWAT 3 , SL EINFELD, 2 HM SIDDONS 1 and VW REES 2 1 Centre for Developmental Psychiatry, Monash University, Clayton, Victoria, 2 School of Psychiatry, University of New South Wales, 3 Department of Medical Genetics, Sydney Children’s Hospital, University of New South Wales, Clayton, NSW, Australia Objective: This study aimed to investigate the role of epilepsy in psychopathology among an epidemiological sample of young people with intellectual disability (ID). The study also compared behavioural and emotional problems in young people on medication to control their epilepsy with those not on medication, and young people with epilepsy who were having current seizure activity with those with no current seizure activity. Methodology: An epidemiological cohort of 392 participants, representative of the general Australian population of young people with ID, were used in the study. One hundred and fifteen individuals from this cohort were identified as suffering from epilepsy. The Developmental Behaviour Checklist was used to measure symptoms of behavioural and emotional disturbance. Results: Results confirmed that young people with ID and epilepsy did not differ from controls without epilepsy on measures of psychopathology. Furthermore, those with epilepsy on medication had no difference in levels of problem behaviours than epileptics not on medication. Conclusions: The results suggest that epilepsy has little or no influence on problem behaviours for young people with ID. Our attempt to understand the pathogenesis of behaviour problems in persons with ID may be better directed towards under- standing genetic mechanisms than epilepsy pathologies. Key words: epidemiological; epilepsy; intellectual disability; psychopathology. Correspondence: Prof. B Tonge, Centre for Developmental Psychiatry, Monash University Medical Centre, Locked Bag no. 29, Clayton, Victoria 3168, Australia. Email: Bruce.Tonge@med.monash.edu.au JN Lewis, BMedSci, Student. BJ Tonge, MD, FRANZCP, Professor and Head. DR Mowat, MB BS, FRACP, Consultant Physician. SL Einfield, MD, FRANZCP, Associate Professor. HM Siddons, Bed, BSc(Hons), Research Assistant. VW Rees, BSc(Hons), PhD, Research Assistant. Accepted for publication 8 November 1999.