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A paper in Scientific Reports found that exposing pregnant mice to mobile phone radiation caused certain brain complications in the unborn rodents. Suggestions that this might have applications to ADHD in human children led the SMC to source comments.
Dr Mischa de Rover, Cognitive Psychologist, Leiden University, The Netherlands, said:
“I performed scientific studies in mice, rats and humans and I found extrapolation of animal data to humans the most difficult part in that area of science. Good animal data is of crucial importance as a starting point for human studies but should never be used as a basis for risk assessment in humans.”
Eric Taylor, Emeritus Professor of Child & Adolescent Psychiatry, Institute of Psychiatry, King’s College London, said:
“This paper does not show any link between radiofrequency exposure and ADHD. The rate of ADHD problems has been steady for more than 20 years (any increase is due to greater recognition), so mobile phones are an unlikely cause.
“Taking animal studies and extrapolating directly to humans requires much more care. The exposure of the animals was very great, and the researchers’ tests of animal memory should not be directly equated to human attention; different species can react differently.”
Professor Malcolm Sperrin, Director of Medical Physics and Clinical Engineering, Royal Berkshire Hospital, said:
“This paper presents work from a highly respected organisation and does bring additional insight into how electromagnetic radiation may affect tissue and its development during gestation. The study is designed appropriately and the conclusions are reasonable. However, the authors repeatedly state that any correlation between the effects on mice during the study and predicted effects on humans are too tenuous to be reasonably claimed.
“This study does not suggest that mobile phones could be the cause of ADHD in humans for several reasons:
“Firstly, the developmental model for mice bears no practical resemblance to humans (19 days gestation versus nine months).
“Secondly, the mice experienced long periods of exposure – in some cases continuously.
“Thirdly, the distance between the source of radiation and the target tissue is not representative of human usage (a few cm as opposed to a metre or so).
“And finally, power density and exposure conditions will be different between the mice and humans.
“It is reasonable to conclude that this study is a worthy step aimed at understanding non-ionising radiation effects, but great caution must be given not to stretch the data too far until more work is done to move toward human equivalent studies.
“It should also be recognised that ADHD is a syndrome which is still being researched and the increase in incidence may arise because of a greater understanding and willingness to describe the occurrence of ADHD. The paper does recognise this and the presence of other contributory factors as possible confounding influences.
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It would be very interesting to identify control groups including those where mobile phone exposure is very limited and to correlate against ADHD in such communities.””
Katya Rubia, Professor of Cognitive Neuroscience, Institute of Psychiatry, King’s College London, said:
“The extrapolation of the behavioural and brain effects of prenatal mobile phone exposure in mice to human ADHD and its increase in our society is alarmist and unjustified. Some enhancement in motor activity in mice is not translatable to the complex human ADHD behaviour characterised by impulsiveness, inattention and motor activity. ADHD is not associated with memory problems, or with decreased anxiety, and the key brain deficits are in the basal ganglia rather than the frontal lobe. While research in humans is warranted there is no convincing evidence in the data to back up such extrapolations to human ADHD.
“This research does not show that mobile phone radiation exposure in utero is linked to ADHD in humans because:
•,The study is in mice and radiation levels are far higher for a mouse foetus than a human foetus.
•,The behavioural outcome features are not comparable to those measured in humans. For example, the mice showed higher motor activity levels and not “hyperactivity”, and the enhanced motoricity does not translate into human ADHD, which is defined as a complex behaviour including hyperactivity, impulsiveness and inattention.
•,Long-term memory that is tested in this study is not associated with ADHD, working memory is but this was not tested in the mice. The introduction mentions working memory impairment in ADHD but then the study measures long-term memory which has nothing to do with working memory. These are two separate functions with dissociated neurobiological substrates. Long-term memory is mediated by the hippocampus and not the frontal lobes, which mediate working memory.
•,Anxiety was reduced in exposed mice, but this is typically higher in ADHD and a key comorbidity.
•,The frontal lobe glutamate system is associated with most psychiatric disorders and there is therefore no specific association between frontal lobe impairment and ADHD. In fact the basal ganglia are the most consistently associated brain areas with ADHD and not the frontal lobes.
“Overall the association between the behavioural and brain complications in rodents due to prenatal mobile phone exposure and human ADHD is clearly over-egged and not justified by the data.”
Philip Asherson, Professor of Molecular Psychiatry and Honorary Consultant Psychiatrist, Institute of Psychiatry, King’s College London, said:
“There are many causes of hyperactivity in mice and most have nothing to do with ADHD. In the paper the mice are more active and less anxious, potentially meaning that they are less anxious (because anxious mice are less active than non-anxious mice). I think it is sufficient to say that the intervention may cause changes in some aspects of behaviour and cognition – and could therefore potentially be linked to development of mental health or cognitive problems later in development. There is nothing here to make any specific link to ADHD or what (in the past) some people referred to as childhood hyperactivity.”
Jim Stevenson, Emeritus Professor of Developmental Psychopathology, University of Southampton, said:
“The study by Aldad et al. concerns the effects on behaviour in mice of exposure to cellular telephone radiation in utero. In introducing their research and in the discussion of their findings the authors propose that the study contributes to our understanding of the origins of hyperactivity and attention-deficit hyperactivity disorder. The paper itself presents no findings on behaviour in children. The authors imply that since a previous study found an association then their work can be seen as suggesting a possible mechanism for the association.
“The paper makes just one reference to a study on humans linking prenatal exposure to cellular radiation to children’s behaviour. The authors of the study referred to conclude: “These associations may be noncausal and may be due to unmeasured confounding.” (Divan et al., 2008).
“In a subsequent paper from this same research group it was concluded that there was “No evidence of an association between prenatal cell phone use and motor or cognitive/language developmental delays among infants at 6 and 18 months of age was observed. Even when considering dose response associations for cell phone use, associations were null.” (Divan et al, 2011).
“The only other study I have been able to locate on this topic in children concluded: “This study gives little evidence for an adverse effect of maternal cell phone use during pregnancy on the early neurodevelopment of offspring.” (Vrijheid et al., 2010).
“So, rather than established link in humans between prenatal exposure and neurodevelopmental disabilities there is to date only little evidence of an association. This makes it irresponsible for the Aldad et al. to speculate about the adverse risks of prenatal exposure from their evidence based on mice. It is known that elevated levels of hyperactivity can arise from genetic and a wide range of environmental factors (for example diet, institutional care and premature birth). It may be that prenatal exposure to cellular phone radiation is another noxious experience contributing to hyperactivity (we just do not know but at present the evidence suggest it is not) but this conjecture cannot be supported by the evidence from mice reported in this paper.”
‘Fetal Radiofrequency Radiation Exposure From 800-1900 Mhz-Rated Cellular Telephones Affects Neurodevelopment and Behavior in Mice’ by Aldad, T. et al., published in Scientific Reports on Thursday 15th March.