In the EU brain disorders were estimated to cost more than any other burden of ill health in 2010 at €789 Billion, in UK at £105 billion.

2 January 2018

INTELLIGENCE AND MENTAL ILL HEALTH 

Low birth weight and pre-term delivery – that is, being born before the pre-natal brain growth thrust is completed – pose a high risk when it comes to neurodevelopmental disorders, which include behavioural issues and IQs lower than the mean.

There is evidence that brain size has been declining for 20,000 years, if not more, with some putting it at a peak 160,000-200,000 years ago – see the skulls from Herto, in Ethiopia. That mental ill health has been going in the opposite direction is illustrated by the rise in cost from EU and UK health audits. In the EU, brain disorders were estimated to cost more than any other burden of ill health, at €386bn. A review of the data, to answer critics, put the cost in 2010 at €789bn. In the UK, it was estimated to be £77bn in 2007, £105bn in 2010 (Department of Health data) and £113bn in 2013 (Wellcome Trust website). We predicted back in the 1970s that this would happen – see Graham Rose in The Sunday Times, 5 November 1972 – based on the evidence available at that time. 

That does not mean mental ill health is only associated with reduced intelligence, nor does it mean that people of high intelligence are free from mental ill health. Although the two are independent properties, it is likely that the rise in mental ill health is related to a decline in brain size, with optimal conditions for development being compromised. Regional deficit or disturbance of pre-natal brain development will have a lifelong impact that is difficult, if not impossible, to subsequently correct. 

Low birth weight and pre-term delivery – that is, being born before the pre-natal brain growth thrust is completed – pose a high risk when it comes to neurodevelopmental disorders, which include behavioural issues and IQs lower than the mean.

In young children with ADHD, for example, it is suggested there is a specific deficit in high-level controlled processing. Evidence of a genetic cause comes from twin studies, which overruled environmental factors. However, the mistake in twin studies is that both are born from the same placenta, so they are subject to the same environmental and nutritional backgrounds during the critical period of brain development.

In autism, likewise, the pre-natal condition is considered a causative factor. Much attention has been given to the possible genetic involvement and the picture looks multi-variant and complex. While the prevalence was estimated at 6 per 1,000 in a population of schoolchildren in 2005, recent studies have gone so far as to estimate autism to affect one child in 38.

This data implies a powerful environmental participation as a dramatic change in genes over this brief time scale is most unlikely.

Cerebral palsy was shown by the European-wide study using MRI not in the main to be due to obstetric mishap, as the lesions identified were present well before the time of birth. After a long study at Guy’s Hospital seeking a genetic-failing explanation, the authors of the European study concluded the cause would be found in infection and or nutrition. In the normal birth-weight range (that is, 3,000g-4.500g) you might have 1 or 2 celebral-palsy births per 1,000 live births. At birth weights below 1,500g (that is, babies likely born below 28 weeks) you could expect 1 in 5.

As with autism (which is also at increased risk with low birth weight) and some other types of mental ill health, you would expect a raised risk of intellectual disability, based on different regions of the brain developing at different times and with different requirements. In that sense, there is a probable but not exclusive link between mental ill health and intelligence. A distortion of brain development in one region is likely to have affected others as well. Hence, instead of autism we now have autistic-spectrum disorders – and it’s the same with ADHD.

Visiting Professor Michael A Crawford, PhD, FRSB, FRCPath, Surgery and Cancer,
Imperial College, London, Chelsea and Westminster Hospital Campus, Room H 3, 34
369 Fulham Road, London SW10 9NH, Mobile 07725 250541 Tel 020 3315 7899. .(JavaScript must be enabled to view this email address); www.imperial.ac.uk/people/michael.crawford


Order of the Rising Sun, 2015, Tokyo, Japan; Chevreul Medal, 2015, Paris, France; Alexander Leaf Distinguished Scientist Award for Lifetime Achievement. ISSFAL, Stellenbosch, South Africa, 2016

References: Fombonne E. Epidemiology of autistic disorder and other pervasive developmental disorders. J Clin Psychiatry. 2005;66 (suppl 10): 3–8. Kim YS., Leventhal BL, Koh YJ, et al. Prevalence of autism spectrum disorders in a total population sample. Am J Psychiatry. 2011;168:904–912.). Human intelligence ‘peaked thousands of years ago and we've been on an intellectual and emotional decline ever since’ by Steve Connor Monday 12 November 2012 17:39 GMT (www.independent.co.uk). Dr Marta Lahr from Cambridge University's Leverhulme Centre for Human Evolutionary Studies presented her findings to the Royal Society in 2013 that brain size of modern-day humans has been shrinking since the beginning of land-based agriculture and animal husbandry 10,000 years ago. http://phys.org/news/2011-06-farming-blame-size-brains.html#jCp

 

 


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