Attention Deficit Hyperactivity Disorder Online Information
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Extracts from Institute of Psychiatry Research Report 2002

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Brain function and genetics in childhood hyperactivity (ADHD)

We have pioneered the application of functional magnetic resonance imaging to the problems and have showed marked underactivity of the brain in ADHD especially in an area involving the frontal lobes and basal ganglia, which normally work to inhibit inappropriate responses. The structure of these areas has proved to be abnormal in a related study: the hyperkinetic children had significant grey matter deficits in right superior frontal gyrus, right posterior cingulate gyrus and the basal ganglia bilaterally (especially right globus pallidus and putamen). This pattern of spatially distributed grey matter deficit in the right hemisphere suggests that ADHD is associated with disruption of a large scale neurocognitive network for attention. The result is under use of these areas, which are activated by normal people when they are carrying out tasks that involve waiting before making a response, or stopping a response when circumstances change. Instead, people with hyperactivity activate a much larger and more diffuse area of the brain, which may not be so well adapted to the job. We have now started extensive molecular genetic and behaviour genetic studies of the cause of the brain abnormalities.

Reliable assessments of hyperactivity

The programme of research on hyperactivity has led to needs for refining clinical diagnosis and research assessment. Schemes to improve clinical diagnosis of ADHD have been worked out and this has included a systematic database (HYPESCHEME) now being used in multinational studies. For older children and adolescents, we have established and tested interview and observational measures, and a set of psychological tests for impulsiveness (the Maudsley Assessment of Response Suppression).

The cognitive basis of hyperactivity

Our neuropsychological research has found difficulties in inhibiting unwanted responses and a preference for immediate gratification rather than waiting for a better reward. We have proceeded to longitudinal analyses of the developmental significance of these neuropsychological alterations. Groups of boys, defined by the presence or absence of hyperactivity, attention problems, and specific reading retardation, were identified in an epidemiological study of 7 year old children. They were examined in detail by means of parental interviews and psychological tests and reassessed 9 years later at the age of 16 18 years. By contrast with inattentive behaviour, which is rather persistent over time, cognitive aspects of attention could change a good deal without altering the psychiatric outcome. Persistent reading disabilities did not lead to the development of hyperactivity de novo or increase the likelihood that hyperactivity, when present, would persist. The high correlation between reading problems and inattentiveness is therefore present from an early stage of development and suggests that there is a common cause.

The treatment of conduct disorders.

We have completed a controlled trial to see whether a behaviourally based group parenting programme, delivered in regular clinical practice, is an effective treatment for antisocial behaviour in children. 141 children aged 3 8 years , who had been referred to clinics with antisocial behaviour, were allocated to parenting groups or waiting list control. The treatment emphasises videotape modelling, engagement with parental emotions, rehearsal of behavioural strategies, and parental understanding of its scientific rationale. These parenting groups effectively reduced serious antisocial behaviour in children in real life conditions.

The cost of antisocial behaviour

We have been able to apply a methodology for ascertaining the cost of services provided for antisocial behaviour in childhood. 10 year old children from an inner London longitudinal study were followed up to adulthood in order to compare the cumulative costs of public services . Costs were 10 times higher than for those with no problems B some 70,000. Antisocial behaviour is a major predictor of how much an individual will cost society. The cost is large and falls on many agencies, yet few agencies contribute to prevention, which could be cost effective. 11 Prevention of challenging behaviours in children with severe learning difficulties. A random allocation controlled trial of behavioural training for parents was completed. The therapy was able to reduce the seventy of the problems that were the targets for treatment. Take up by families was quite good providing it was offered in a flexible and individually planned way. By contrast, a group approach was much less popular among the families especially ethnic minority families. Our evaluated behavioural training is now being applied by a special clinic and taught to services elsewhere.

Attachment and disruption of attachment

The attachment of children to their parents is a major influence on human development, yet relatively little is known about how individual differences in attachment come about. The degree to which individual differences in child parent attachment were mediated by genetic, shared environmental, or nonshared environmental influences was therefore investigated in 110 preschool aged twin pairs . Observational measures found that the degree of concordance was equally high in monozygotic and dizygotic twin pairs (70% and 64%, respectively). Twin similarity on a continuous measure of attachment security was .48 for monozygotic and .38 for dizygotic twin pairs, indicating only a modest role for genetic influence but a significant effect for both shared and nonshared environment.

Dreadful deprivation was inflicted on children in the orphanages of Romania, and we have been working with a cohort of such children who were adopted into this country. We have found, for example, that the harm that is done is proportional to the length of time for which the children have been deprived. It has also turned out that the harm can be specific: attachment problems, inattention/overactivity, quasi autistic features and cognitive impairment were specifically associated with institutional privation, but emotional difficulties, poor peer relationships and conduct problems were not.

Many of the children rescued from privation made good adjustments, and there was a good deal of variation between individuals. It is therefore important to know whether their recovery is a function of the families into which they are adopted. Careful observation by investigators who did not know the child's background suggested that this was not really true: the quality of the parent child relationship was associated chiefly with how long the deprivation had lasted and how much cognitive/developmental delay the child showed. There was more likely to be a positive change in the parentchild relationship if the child's cognitive development had advanced well. The direction of effects appeared to be primarily that the child influences the parents.

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