Implications

Why is there research and clinical interest in determining causal links between genetic syndromes and behaviour? The benefits of behavioural phenotype work include benefits to the individuals themselves and their families and to professionals working with individuals with genetic syndromes. There are also more wide reaching benefits for the research community as a whole. Prior to discussing the benefits of the behavioural phenotype approach in more detail, the drawbacks to such an approach are considered.

Drawbacks to the approach were outlined by O’Brien (1999) in a symposium on behavioural phenotype research given to the Royal Society of Medicine.

One drawback might be that those individuals with a genetic syndrome may be somewhat stigmatised due to the behavioural difficulties known to be associated with that disorder. Another drawback might be that it encourages therapeutic nihilism. A therapist may consider behaviours that have a strong genetic influence not possible to treat using conventional behavioural techniques. Describing individuals with a disorder as having an increased propensity to show certain behavioural or emotional difficulties may lead to a self-fulfilling prophecy where individuals with that genetic syndrome are more likely to show the difficulties because they are expected to. Some may deem the whole process of describing behaviours associated with genetic disorders unnecessary since it is already known that there are genetic influences all around us. These are all legitimate concerns regarding the field of behavioural phenotypes however consideration of the benefits of such investigations seems to outweigh these potential disadvantages. I now turn to discuss some of these benefits.

Careful delineation of behaviours associated with a disorder will lead to improved diagnosis. Even if a genetic test exits for a particular syndrome, it is unlikely to be part of routine screening, as many genetic disorders are exceedingly rare. Knowledge about the developmental manifestations of specific disorders allows for the identification of areas that warrant close monitoring for early signs of deviations from typical development (Finegan, 1998). Observation of a particular deviant pattern of behaviour may point to a particular genetic disorder and to a genetic test, leading to earlier diagnosis and maybe early intervention. Some genetic disorders are treatable if diagnosed early. For example, PKU can be effectively treated with medication following the confirmation of the genetic disorder early in life. For genetic disorders where no such treatment currently exists, diagnosis is still advantageous. It can provide relief to parents from feelings of guilt that they are to blame for their child's difficulties (Turk & Hill, 1995). Following a diagnosis genetic counselling can proceed and it allows for membership into a parental support network.

Knowledge of the specific pattern of strengths and weaknesses in individuals with genetic disorders permits for information about prognosis and management to be provided to parents. Of course, not all children with a particular disorder will show the same problems, but information about the course of the disorder can help professionals manage parents’ expectations for their child (Dykens, 1999).

There are intervention advantages. Clearer understanding of the behaviours associated with specific syndromes may suggest particular therapeutic interventions are required. For example, individuals with Williams syndrome are reported to be sociable and have particularly keen interests in others. Therefore these individuals may be well suited to group therapies (Dykens, 1999). In contrast, individuals with Fragile-X are reported to be prone to shyness and social anxiety. Therefore, these individuals may respond better to individualised approaches to therapy (Dykens 1995). The development of intervention strategies for individuals with particular disorders will lead to the sharing of information about appropriate educational and behavioural management approaches for specific syndromes. Clinicians will be able to draw on this information when designing individual case management plans (Dykens, 1999).

Stating that a behaviour is a behavioural phenotype implies that it is, to some extent, genetically mediated. It is unlikely that the knowledge that a behaviour comprises a behavioural phenotype would lead to reduced therapeutic input. Although, the extent to which a behaviour is genetically mediated may have implications for the choice of intervention strategy. For example, if a behaviour is largely biologically mediated, pharmacological therapy may be the most appropriate choice of intervention. Whereas, if a behaviour is largely environmentally mediated, behavioural intervention may be most appropriate. If a behaviour is associated with a genetic disorder it does not mean that behavioural intervention is not appropriate but alerts the clinician of the need to consider how biological and behavioural factors are related (Holland, 1999), Knowledge of behavioural phenotypes can be used

to guide treatment priorities and provide additions to standard clinical care (Dykens, 1995a).

There is also hope that studying the links between genetic anomalies and the resulting behavioural profile may enhance our understanding of typical as well as atypical development. Through the neuroimaging of individuals with genetic syndromes with associated specific patterns of cognitive and behavioural functioning, it may be possible to guide hypotheses about brain- behaviour relations (Finegan, 1998). These investigations are unlikely to inform directly about brain-behaviour relations in typical development. The brains of those with genetic syndromes may have developed differently from conception (Paterson, Brown, GsodI, Johnson, & Karmiloff-Smith, 1999). However, patterns of atypical development could be used to build hypotheses regarding normal development which could then be tested in typically developing individuals (e.g., Rae et al. (1998) hypothesised that the cerebellum might be involved in cognition following their findings on individuals with Williams syndrome).

The study of behavioural phenotypes may provide information about the genetic basis of behaviour. Molecular genetic investigations are being used to identify chromosome microdeletions which can be linked to specific behavioural characteristics. There is increasing interest in research looking at genotype-phenotype correlations. However, as Flint (1996) points out, the belief that links can be made between specific genes and behaviour is founded on two assumptions. First, the pathway from genetic anomaly to behaviour is short and direct enough to describe. Second, that phenotypes bear a meaningful relation to normal behaviour. Flint proposes that behaviour is often an outcome of a long and complex pathway and that characterisation of a single mutant gene will not be enough to account for the behavioural phenotype. He also makes the point that the behaviours observed in atypical development could be phenocopies of the behaviour seen in individuals with typical development. They may appear to be the same behaviour but have a different biological aetiology. If behavioural phenotypes are to be used to

investigate gene-behaviour relations, detailed and careful characterisation of the behavioural phenotype is vital. It is important to determine whether a particular behaviour is truly specific to a genetic syndrome. If the behaviour is specific there is an increased chance of being able to demonstrate the genetic underpinning of that behaviour. Careful delineation of behavioural phenotypes may be the first step towards determining the biological underpinnings of behaviour (Flint, 1996).