Gregory OBrien is Professor of Developmental Psychiatry at the University of Northumbria and Northgate Hospital, Morpeth NE61 3BP, UK. Email: greg.o'brien{at}nap.nhs.uk). His research interests include outcome studies in intellectual disability and the biological basis of behaviour disorder in developmental disability.
Behavioural phenotypes are patterns of behaviour that present in syndromes caused by chromosomal or genetic abnormalities. They have both physiological and behavioural manifestations with distinctive social, linguistic, cognitive and motor profiles. Their course is not static. Presentation typically varies according to level of learning disability and a host of environmental, developmental and therapeutic influences, and it changes with increasing age.