Behavioural Phenotypes and their Measurement

THE TERM 'behavioural phenotype' has only recently come into regular use in developmental and behavioural paedi- atrics', but already it is becoming part of mainstream thinking. There are several reasons for this. First, the new molecular biology offers opportunities to identify the genetic contribution to certain human traits. In the field of human behaviour, any such insights rely for their validity on the confidence we may hold in our accounts of behavioural observation2; this is the province of behavioural phenotypy. Second, the practical and scientific importance of this work has led to the establishment of the Society for the Study of Behavioural Phenotypes, an international association of clinicians and scientists interested in behavioural genetics and behavioural phenotypy. Third, the current rapid expansion of support societies for the parents and families of people affected by disabling conditions and mentally handicapping syndromes is acting as another major catalyst to research in this area. Good examples include the work on tuberous

sclerosis3, Williams syndrome' and Prader-Willi syndrome', all of which have involved the collaboration of the respective support society.

This collaboration operates in three ways, and reveals much about the origins, nature, direction and standing of the work: (1) often it has been the initial anecdotal evidence of these societies- that certain behavioural problem@) occur frequently in children afflicted by some syndromes-which has both initiated and given direction to the research; (2) in many cases the societies have greatly facilitated data collection-while the clinical practice of even the most motivated and interested researcher is unlikely to result in an extensive series of people with some of the more rare syndromes, these societies are in a unique position to facilitate contact with large samples; and (3) as a measure of the importance of this type of research in the eyes of the parents of affected children, there are already instances of research being funded by such groups.

Therefore, it seems likely that, at least for the foreseeable future, we will see more and more examples of research in the area of behavioural phenotypy. Given this state of affairs, a few timely notes of caution should be sounded.

It is important that we are clear just what we mean by the term 'behavioural phenotype'. Conceptually, this is based

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on the 'phenotype as expression of the genotype'. It should therefore be reserved for the behaviours which are particularly common in people affected by a given genetic condition. It should not be used as an alternative to behavioural syndrome or psychiatric diagnosis. For example autism is not 'a behavioural phenotype', bct autism does feature in the behavioural phenotype of certain syndromes, notably fragile x' and tuberous sclerosis3. This much is fairly clear-cut. The issue becomes more complex, and probably more contentious, when writers comment on the behavioural phenotype of learning disability or of language disorder6. While it is true, of course, that some behavioural problems are more common among people with more severe learning disabilities than others', it would seem sensible not to over-use the term in this way, but to reserve it for the purpose originally envisaged', and now generally accepted.

Alongside this policy of exclusivity of the behavioura! phenotype concept, there is one research strategy which is, at least on first impressions, at variance with the area of inquiry as outlined above. This is the study of case series in which a biologically distinct syndrome is \not yet apparent on some physically identifiable criteria, but in which behavioural observations-possibly together with other putative phenotypic findings-suggest a syndrome. One important contemporary example is Rett syndrome'. Interestingly, in certain well-documented conditions- including Lesch-Nyhan* and Prader-Willi syndromes-it was by such initial detailed clinical observation of idiosyncratic behaviours that a distinct syndrome was suggested, and this in turn has facilitated the research which has yielded the biological markers for these disorders. Research of this type is of particular importance and is within the domain of behavioural phenotypy, relying as it does on detailed clinical observation.

Just as factors other than the gene are crucial in the aetiology of psychiatric disorders in general, so must it be remembered that the behavioural problems of children afflicted by congenital syndromes-particularly those that result in a significant degree of

learning disability-are the result of the complex interplay of a variety of in- fluences on behaviour. Therefore, before it can be stated confidently that a given psychiatric disorder (such as autism) is a feature of the behavioural phenotype of a congenital syndrome (such as fragile x), research mush take into account the other factors of established importance in the aetiology of that psychiatric disorder. In other words, the co-association of a particular behavioural constellation and a given congenital syndrome does not of itself amount to the clarification of a behavioural phenotype. However, where the association is a strong one, and particularly where the set of behavioural problems is otherwise uncommon, there is clearly the need for further inquiry.

On a practical note, the identification of a behavioural phenotype should not be regarded either by clinicians or carers as cause for despair or resignation. Rather, the recognition that certain syndromes result in particular behavioural problems, whether frequently or invariably, is another step toward an holistic approach to the understanding of behaviour. For example the diagnosis of Rett syndrome gives some insight into the cause and nature of certain repetitive, and in some cases self-injurious, movement dis- orders'. However, this should not in turn result in the cessation of treatment efforts-employing, for example, stan- dard methods of behavioural analysis and intervention-but should alert the clinician to the likely need for particular care in designing the case management plan.

Finally, behavioural phenotypy research needs to have a clear direction, and to use consistent and compatible methodologies. Toward these ends, two recent pub- lications of the Society for the Study of Behavioural Phenotypes are timely.* First, a guide to the relevant schedules"+ 'I is now available. This provides a uniformly structured, detailed critique of over 50 measurement tools, including comments on their applicability to different types of

*For further information about behavioural phenotypes and the work of the Society for the Study of Behavioural Phenotypes, contact Dr. J . Dennis, SSBP Secretary, Park Hospital, 'Oxford, U.K.

subject groups, study designs and research strategies, together with in- formation on relevant reliability and validity studies, and other statistical and psychometric information. Second, because of the importance of obtaining comparative cross-syndrome data, a questionnaire has been developed specifically for this purpose. Researchers who use this instrument contribute to, and consequently are entitled to access, an evolving database of the behavioural phenotypes of a wide variety of congenital disabling conditions. In addition, they can be assured that they are employing an instrument which is not only acceptable from a scientific standpoint, but also has already proven to be sensitive to the difficulties experienced by the parents and families of children with such conditions.

GREGORY O’BRIEN Section of Developmental Psychiatry, Department of Psychiatry, University of Cambridge, Addenbrooke ’s Hospital, Cambridge CB2 2QQ.

References 1. Gillberg, C., Ohlson, V.-A.. Wahlstrom, J.,

Steffenburg, S., Blix, K . (1988) ‘Monozygotic

25th Congress of European Society of Paediatric Neurosurgery Berlin, 319 May to 2nd June 1992

Information from Professor Mario Brock, President of the Congress, Department of Neurosurgery, Free University of Berlin, Hindenburgdamm 30, W-IOOO Berlin 45, Germany. Tel.: (49) 30 798 2531; Fax: (49) 30 798 3569.

NATO Advanced Research Workshop and Joseph Roger Day Marseille, 23rd to 27th June 1992

The Fourth International Workshop on Childhood- Epilepsies will be held on 23rd to 26th June. It is being organised by Charlotte Dravet, Centre Saint- Paul (Marseille, France), Fritz Dreifuss, Charlottes- ville (Virginia, USA) and Cesare Lombroso, Boston (Massachusetts, USA). The topic is ‘Epilepsies and generalised epileptic syndromes before the age of six’. This workshop will be foilowed on 27th June by a scientific day in honour of Joseph Roger. For further information and registration details, contact Dr. Michelle Bureau, AREP, 300 Bd. de Sainte- Marguerite, 13009 Marseille, France. Tel.: (33) 91 75 13 40.

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female twins with autism and the fragile X syndrome (AFRAX). Journal of Child Psychology and Psychiatry. 29, 447-45 I . Rutter, M., Bolton, P., Harrington, R. Le Couteur, A., MacDonald, H., Simonoff, E. (1990) ‘Genetic factors in child psychiatric disorders. I : A review of research strategies.’ Journal of Child Psychology and Psychiatry,

Hunt, A., Dennis, J . (1987) ‘Psychiatric disorder among children with tuberous sclerosis.’ Developmental Medicine and Child Neurology. 29, 190- 198. Udwin, 0. (1990) ‘A survey of adults with Williams syndrome and idiopathic infantile hypercalcaemia.’ Developmental Medicine and Child Neurology, 32, 129- 14 I .

Clarke, D. J., Waters, J., Corbett, J. A. (1989) ‘Adults with Prader-Willi syndrome.’ Journal of the Royal Society of Medicine, 82, 21-24.

Siggers, D. C. (1977) ‘Human behavioural genetics.’ Developmental Medicine and Child Neurology, 19, 818-826. (Annotation.)

Fraser, W. I . , Leudar, I . , Gray, J. (1986) ‘Psychiatric and behavioural disturbance in mental handicap.’ Journal of Mental Deficiency Research, 30, 49-57.

Nyhan, W. L. (1972) ‘Behavioural phenotypes in organic genetic disease.’ Pediatric Research,

Hagberg, B.. Witt-Engerstrom, I . (1986) ‘Rett syndrome: a suggested staging system for describing impairment profile with increasing age towards adolescence.’ American Journal of Medical Genetics, 24, 47-59.

Society for the Study of Behavioural Phenotypes (1991) Behavioural Measurement in Mental Handicap. Oxford: SSBP Publications.

O’Brien, G. (1992) ‘Behavioural phenotypy in developmental psychiatry.’ European Child and Adolescent Psychiatry, Suppl. I , 1-61.

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World Congress on Rett Syndrome Antwerp, 7th to 10th October 1992

The Belgian Rett Syndrome Association invites all parents, doctors, psychologists, therapists and teachers to this congress, which will be held in the Auditorium, County Hall, Antwerp, under the patronage of the Governor of Antwerp, A. Kinsbergen. For further information and registration details, contact Peter Vanherck, Lil 26, B-2450 Meerhout, Belgium. Tel.: (14) 30 94 94; Fax: (14) 30 31 57.

Corrigendum Two errors occurred %in the paper ‘Oral-motor dysfunction and feeding disorders of infants with Turner syndrome’ by Mathisen et al. (DMCN, 34, 141-149). The footnote to Table I should read ‘ + =difficulty reported; - = n o difficulty reported’, and the correct reference for Tanner 1989 (p. 145) is Tanner, J. M., Thompson, A. M. (1970) ‘Standards for birthweight at gestation periods from 32 to 47 weeks, allowing for maternal height and weight. Archives of Disease in Childhood, 45, 566-569. 367