Objective To summarise the effects of anthelmintic drug treatment on growth and cognitive performance in children. Results Thirty randomised controlled trials in more than 15 000 children were identified. Effects on mean weight were unremarkable, and heterogeneity was evident in the results. There were some positive effects on mean weight change in the trials reporting this outcome: after a single dose (any anthelmintic) the pooled estimates were 0.24 kg (95% confidence interval 0.15 kg to 0.32 kg; fixed effects model assumed) and 0.38 kg (0.01 kg to 0.77 kg; random effects model assumed). Results from trials of multiple doses showed mean weight change in up to one year of follow up of 0.10 kg (0.04 kg to 0.17 kg; fixed effects) or 0.15 kg (0.00 to 0.30; random effects). At more than one year of follow up, mean weight change was 0.12 kg (−0.02 kg to 0.26 kg; fixed effects) and 0.43 (−0.61 to 1.47; random effects). Results from studies of cognitive performance were inconclusive. Conclusions There is some limited evidence that routine treatment of children in areas where helminths are common has effects on weight gain, but this is not consistent between trials. There is insufficient evidence as to whether this intervention improves cognitive performance. Data sources

Forty‐two infants (20 males, 22 females) with classical phenylketonuria (PKU) entered a prospective, double‐blind, randomized study to investigate the effects on biochemical and physiological outcomes of a phenylalanine‐free infant formula containing a fat blend supplemented with the long‐chain polyunsaturated fatty acids (LC‐PUFA), docosahexaenoic acid (DHA, C22:6n‐3), and arachidonic acid (AA, C20:4n‐6). Between entry and 20 weeks (entry and 1y) of age, median DHA levels in erythrocyte membrane phospholipids decreased by 15% (22%) in the LC‐PUFA supplemented group (n=21) and by 61% (64%) in the control group (p<0.001; n=18). A dietary supply of LC‐PUFA in infants with PKU prevents the decline in DHA levels associated with a diet supplying minimal sources of LC‐PUFA. DHA status in turn, independent of diet, may influence the maturation of the visual system in infants with PKU.

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An hypothesis is presented about the nature of behavioural tolerance in animals to stimulant drugs. It is suggested that, in many behavioural procedures, tolerance is due to behavioural adaptation to those drug effects which cause disruption of ongoing rewarded behaviour. This unitary hypothesis accounts for the available data on tolerance and cross-tolerance to stimulants more effectively than all of the other more conventional explanations which are based upon dispositional or functional concepts, the most common of which are described, evaluated, and found to be inadequate. Furthermore, it is suggested that attempts to explain tolerance in terms of changes in synaptic functioning are subject to very considerable problems of interpretation and that an analysis of behavioural mechanisms may be of greater value in understanding the process of behavioural tolerance. Evidence for the basic behavioural hypothesis is outlined in some detail, and a theoretical justification presented for its major assumptions. Operant studies of chronic stimulant effects on behaviour have often produced very complex patterns of data, considerable differences being reported both between subjects and between studies. A speculative model is presented which attempts to account for this pattern of data in tolerance studies.

Aim-Mildly depressed IQ is common in treated phenylketonuria. This study explored whether a particular intellectual ability profile typifies early and continuously treated phenylketonuria and whether component skills comprising the IQ relate to socioeconomic and treatment factors. Methods-IQ scores were collected retrospectively from variants of the "Wechsler intelligence scale for children" performed at age 8 on 57 children with early treated, classic phenylketonuria. The mental ability pattern underlying IQ was investigated by analysing subscale and subtest scores and dietary factors, such as historical phenylalanine blood concentrations. Results-The children's mean full scale IQ of 91.11 was significantly below the healthy population norm. There was a significant discrepancy between their mean verbal IQ (94.65) and mean performance IQ (89.42), suggestive of a spatial deficit, but the data did not support a biochemical or sociological explanation. Individual Wechsler subtests had no distinctive pattern. Phenylalanine control at age 2 was predictive of overall IQ. At this age, children with annual median phenylalanine < 360 µmol/litre (recommended UK upper limit) had a mean IQ 10 points higher than those above. Conclusions-Early and continuous treatment of phenylketonuria does not necessarily lead to normalisation of overall IQ. Verbal intelligence in the primary school years appears to normalise if blood phenylalanine is maintained below 360 µmol/litre in infancy, but spatial intelligence may remain poor. However, the discrepancy in skill development is not the result of social status or treatment variables. Perhaps weak spatial intelligence is an ancillary eVect of a protective rearing style occasioned by the dietary treatment regimen. (Arch Dis Child 2000;82:209-215) Keywords: phenylketonuria; intelligence quotient; dietary treatment; policy Since the initiation in the 1960s of mass screening for phenylketonuria (McKusick 261600), treatment outcome during the school age period has been assessed principally by the "Wechsler intelligence scale for children" (WISC). 1 In general, outcome studies have related Wechsler IQ to independent variables such as severity, age of commencement of dietary phenylalanine restriction, phenylalanine range during treatment, and age of dietary discontinuation. Most studies have selected the overall or full scale IQ as the dependent variable, this paradigm typifying the approach taken by national collaborative studies in the UK and the USA. 2 3 Although the full scale IQ provides a convenient summary of intellectual development, it obscures the richness of information about individual or group profiles of mental skill inherent in WISC assessments. To our knowledge, among studies of treatment factors in phenylketonuria, there are no reports concerning the 10 subtest scores on which full scale and subscale IQs are based, despite their necessarily having been collected in the course of testing. Thus, the question of whether a particular WISC subtest profile characterises t...