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Encyclopedia > Health and intelligence

Several factors can lead to significant cognitive impairment, particularly if they occur during pregnancy and childhood when the brain is growing and the blood-brain barrier is less effective. Developed nations have implemented several health policies regarding nutrients and toxins known to influence cognitive function. These include laws requiring micronutrient fortification of certain food products and laws establishing safe levels of pollutants (e.g. lead, mercury, and organochlorides). Comprehensive policy recommendations targeting reduction of cognitive impairment in children have been proposed.[1] Freeze-fracture morphology of the blood-brain barrier of a rat The blood-brain barrier (abbreviated BBB, not to be confused with the blood-cerebrospinal fluid barrier, a function of the choroid plexus) is a membrane that controls the passage of substances from the blood into the central nervous system. ...

Improvements in nutrition, and in public policy in general, have been implicated in worldwide secular IQ increases (the Flynn effect). The Flynn effect is the year-on-year rise of IQ test scores, an effect seen in most parts of the world, although at greatly varying rates. ...



Micronutrient deficiencies (e.g. in iodine and iron) influence the development of intelligence and remain a problem in the developing world. Policy recommendations to increase availability of micronutrient supplements have been made and justified in part by the potential to counteract intelligence-related developmental problems. For example, see the Copenhagen consensus, and its statement on hunger.[2] General Name, Symbol, Number iodine, I, 53 Chemical series halogens Group, Period, Block 17, 5, p Appearance violet-dark gray, lustrous Atomic mass 126. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... Copenhagen Consensus is a project which seeks to establish priorities for advancing global welfare using methodologies based on the theory of welfare economics. ...

A joint statement on vitamin and mineral deficiencies says that the severity of such deficiencies "means the impairment of hundreds of millions of growing minds and the lowering of national IQs."[3] Lack of both iodine and iron has been implicated in impaired brain development, and this can affect enormous numbers of people: it is estimated that 2 billion people (one-third of the total global population) are affected by iodine deficiency, including 285 million 6- to 12-year-old children. In developing countries, it is estimated that 40% of children aged 4 and under suffer from anaemia because of insufficient iron in their diets. Studies investigating whether cognitive function in iron-deficient children can be improved with iron supplements have produced mixed results but the approach is considered promising.[4]

Vitamin-mineral supplementation may have an effect also in the developed world. A study giving such supplementation to "working class," primarily Hispanic, 6-12 years old children in the United States for 3 months found an average increase 2 to 3 IQ points. Most of this can explaind by the very large increase for a subgroup of the children, presumably because these were not adequately nourished unlike the majority. The study suggests that parents of schoolchildren whose academic performance is substandard would be well advised to seek a nutritionally oriented physician for assessment of their children's nutritional status as a possible etiology.[5]

The longstanding belief that breastfeeding correlates with an increase in the IQ of offspring was challenged in a 2006 paper published in the British Medical Journal. The results indicated that mother's IQ, not breastfeeding, explained the differences in the IQ scores of offspring. The results of this study argued that prior studies had not allowed for the mother's IQ. Since mother's IQ was predictive of whether a child was breastfed, the study concluded that "breast feeding [itself] has little or no effect on intelligence in children." Instead, it was the mother's IQ that had a significant correlation with the IQ of her offspring, whether the offspring was breastfed or was not breastfed.[6] The study has been subject to various criticisms.[7] Another study found a positive effect of breastfeeding also after controlling for parental IQ.[8] Breastfeeding an infant Symbol for breastfeeding (Matt Daigle, Mothering magazine contest winner 2006) Breastfeeding is the process of a woman feeding an infant or young child with milk from her breasts. ...

More speculatively, other nutrients may prove important in the future. Fish oil supplement to pregnant and lactating mothers has been linked to increased cognitive ability in one study.[9] Vitamin B12 and folate may be important for cognitive function in old age.[10] Cobalamin or vitamin B12 is a chemical compound that is also known as cyanocobalamine. ... Folic acid (the anion form is called folate) is a B-complex vitamin (once called vitamin M) that is important in preventing neural tube defects (NTDs) in the developing human fetus. ...


Toxins, such as lead and mercury, can have serious cognitive effects. Policies to manage lead differ between nations, particularly between the developed and developing world.[11] Use of leaded gasoline has been reduced or eliminated in most developed nations, and lead levels in US children have been substantially reduced by policies relating to lead reduction.[11] Even slightly elevated lead levels around the age of 24 months are associated with intellectual and academic performance deficits at age 10 years.[12] General Name, Symbol, Number lead, Pb, 82 Chemical series poor metals Group, Period, Block 14, 6, p Appearance bluish white Atomic mass 207. ... General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery Atomic mass 200. ... Gasoline, also called petrol, is a petroleum-derived liquid mixture consisting mostly of hydrocarbons and enhanced with benzene or iso-octane to increase octane ratings, used as fuel in internal combustion engines. ...

Certain, at least previously, widely used organochlorides, such as dioxins, DDT, and PCB, have been associated with cognitive deficits.[13] An organochloride is an organic compound containing at least one covalently bonded chlorine atom. ... Dioxins form a family of toxic chlorinated organic compounds that bioaccumulate in humans and wildlife due to their fat solubility. ... DDT was the first modern pesticide and is arguably the best known organic pesticide. ... PCB may refer to: Brazilian Communist Party (in Portuguese, Partido Comunista Brasileiro) Communist Party of Bolivia (in Spanish, Partido Comunista de Bolivia) Pakistan Cricket Board PCBoard, a bulletin board system software Police Complaints Board, which oversaw the system for handling complaints made against police forces in England and Wales until...

Fetal alcohol exposure, causing Fetal alcohol spectrum disorder, is one of the leading known causes of mental retardation in the Western world. Fetus at eight weeks A fetus (alternatively foetus or fœtus) is an embryo in later stages of development, from the third month of pregnancy until birth in humans. ... Functional group of an alcohol molecule. ... This baby has FASD. Fetal alcohol spectrum disorder (FASD) describes a spectrum of permanent and often devastating birth-defect syndromes caused by maternal consumption of alcohol during pregnancy. ...

Maternal tobacco smoking during pregnancy is associated with increased activity, decreased attention, and diminished intellectual abilities.[14] However, a recent study finds that maternal tobacco smoking has no direct causal effect on the child's IQ. Adjusting for maternal cognitive ability as measured by IQ and education eliminated the association between lower IQ and tobacco smoking.[15] But another study instead looking at the relationship between environmental tobacco smoke exposure, measured with a blood biomarker, and cognitive abilities among U.S. children and adolescents 6–16 years of age, found an inverse association between exposure and cognitive deficits among children even at extremely low levels of exposure. The study controlled for sex, race, region, poverty, parent education and marital status, ferritin, and blood lead concentration.[16] Species Nicotiana acuminata Nicotiana alata Nicotiana attenuata Nicotiana benthamiana Nicotiana clevelandii Nicotiana excelsior Nicotiana forgetiana Nicotiana glauca Nicotiana glutinosa Nicotiana langsdorffii Nicotiana longiflora Nicotiana obtusifolia Nicotiana paniculata Nicotiana plumbagifolia Nicotiana quadrivalvis Nicotiana repanda Nicotiana rustica Nicotianasuaveolens Nicotiana sylvestris Nicotiana tabacum Nicotiana tomentosa Ref: ITIS 30562 as of August 26, 2005...

Healthcare during pregnancy and childbirth

Healthcare during pregnancy and childbirth, access to which is often governed by policy, also influences cognitive development. Preventable causes of low intelligence in children include infectious diseases such as meningitis, parasites, and cerebral malaria, prenatal drug and alcohol exposure, newborn asphyxia, low birth weight, head injuries, and endocrine disorders. A direct policy focus on determinants of childhood cognitive ability has been urged.[1] Meningitis is inflammation of the meninges, caused by bacteria or viral infections elsewhere in the body that have spread into the blood and into the cerebrospinal fluid (CSF). ... Suffocation redirects here, for the band, see Suffocation (band). ... Low birth weight is defined by the World Health Organization (WHO) as a fetus who is delivered to a reproductive female at the end of a pregnancy at a weight of < 2500 grams (WHO, 1969). ...


A recent theory suggests that early childhood stress may affect the developing brain and cause negative effects.[17]

Tropical infectious diseases

On the disease front, malaria affects 300–500 million persons each year, mostly children under the age of 5 in Africa, causing widespread anemia during a period of rapid brain development and also direct brain damage from cerebral malaria to which children are more vulnerable.[18] Policies aimed at malaria reduction may have cognitive benefits. It has been suggested that the future economic and educational development of Africa critically depends on the eradication of malaria. Malaria is a vector-borne infectious disease that is widespread in tropical and subtropical regions. ... A world map showing the continent of Africa. ... Anemia (AmE) or anaemia (BrE), from the Greek () meaning without blood, refers to a deficiency of red blood cells (RBCs) and/or hemoglobin. ...

Roundworms infect hundreds of millions of people. There is evidence that high intensities of worms in the intestines can affect mental performance.[19] Classes Adenophora    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The roundworms (Phylum Nematoda) are one of the most common phyla of animals, with over 20,000 different described species. ...

Association with other diseases

There are numerous diseases affecting the central nervous system which can cause cognitive impairment. Many of these are associated with aging. Some common examples include Alzheimer's disease and Multi-infarct dementia. Multi-infarct dementia, also known as vascular dementia, is a form of dementia resulting from brain damage caused by stroke or transient ischemic attacks (also known as mini-strokes). ...

Persons with a higher IQ have generally lower adult morbidity and mortality. This may be because they better avoid injury and take better care of their own health, or alternatively may be due to a slight increased propensity for material wealth. Post-Traumatic Stress Disorder, severe depression, and schizophrenia are less prevalent in higher IQ bands. The Archive of General Psychiatry published a longitudinal study of a randomly selected sample of 713 study participants (336 boys and 377 girls), from both urban and suburban settings. Of that group, nearly 76 percent had suffered through at least one traumatic event. Those participants were assessed at age 6 years and followed up to age 17 years. In that group of children, those with an IQ above 115 were significantly less likely to have Post-Traumatic Stress Disorder as a result of the trauma, less likely to display behavioral problems, and less likely to experience a trauma. The low incidence of Post-Traumatic Stress Disorder among children with higher IQs was true even if the child grew up in an urban environment (where trauma averaged three times the rate of the suburb), or had behavioral problems.[20] On the other hand, higher IQ shows a higher prevalence of those conditioned with Obsessive Compulsive Disorder.[21] Post-traumatic stress disorder (PTSD) is a term for certain psychological consequences of exposure to, or confrontation with, stressful experiences that the person experiences as highly traumatic. ... Clinical depression (also called major depressive disorder, or sometimes unipolar when compared with bipolar disorder) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individuals social functioning and/or activities of daily living. ... For other things named OCD, see OCD (disambiguation). ...

Major depression, affecting about 16% of the population on at least one occasion in their lives and the leading cause of disability in North America, may give symptoms similar to dementia. Patients treated for depression score higher on IQ tests than before treatment.[22][23] It is common to feel sad, discouraged , or down once in a while, and anyone in this state might say they are suffering from depression. ...

Research in Scotland has shown that a 15-point lower IQ meant people had a fifth less chance of seeing their 76th birthday, while those with a 30-point disadvantage were 37% less likely than those with a higher IQ to live that long.[24] In addition, a study of 11,282 individuals in Scotland who took intelligence tests at ages 7, 9 and 11 in the 1950s and 1960s, found an "inverse linear association" between childhood intelligence and hospital admissions for injuries in adulthood. The association between childhood IQ and the risk of later injury remained even after accounting for factors such as the child's socioeconomic background.[25]

A decrease in IQ has also been shown as an early predictor of late-onset Alzheimer's Disease and other forms of dementia. In a 2004 study, Cervilla and colleagues showed that tests of cognitive ability provide useful predictive information up to a decade before the onset of dementia.[26] Dementia (from Latin de- apart, away + mens (genitive mentis) mind) is the progressive decline in cognitive function due to damage or disease in the brain beyond what might be expected from normal aging. ...

However, when diagnosing individuals with a higher level of cognitive ability, in this study those with IQ's of 120 or more,[27] patients should not be diagnosed from the standard norm but from an adjusted high-IQ norm that measured changes against the individual's higher ability level.

In 2000, Whalley and colleagues published a paper in the journal Neurology, which examined links between childhood mental ability and late-onset dementia. The study showed that mental ability scores were significantly lower in children who eventually developed late-onset dementia when compared with other children tested.[28]

See also

// Brain size The correlation between brain size and IQ seems to hold for comparisons between and within families (Gignac et al. ...


  1. ^ a b Olness, K. "Effects on brain development leading to cognitive impairment: a worldwide epidemic," Journal of Developmental and Behavioral Pediatrics 24, no. 2 (2003): 120–30.
  2. ^ Behrman, J.R., Alderman, H., and Hoddinott, J., "Hunger and Malnutrition," Copenhagen Consensus 2004.
  3. ^ UNICEF and The Micronutrient Initiative, "Vitamin & Mineral Deficiency: A Global Progress Report," March 2004.
  4. ^ Saloojee, H. and Pettifor, J., Iron deficiency and impaired child development," BMJ 323 (December 2001): 1377–78
  5. ^ The effect of vitamin-mineral supplementation on the intelligence of American schoolchildren: a randomized, double-blind placebo-controlled trial J Altern Complement Med. 2000 Feb;6(1):31-5.
  6. ^ Geoff Der, G David Batty, Ian J. Deary (2006). Effect of breast feeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis (Abstract). British Medical Journal.
  7. ^ Rapid Responses
  8. ^ Influence of breast-feeding and parental intelligence on cognitive development in the 24-month-old child. Clin Pediatr (Phila). 2004 Oct;43(8):753-61. Influence of breast-feeding and parental intelligence on cognitive development in the 24-month-old Gomez-Sanchiz M, Canete R, Rodero I, Baeza JE, Gonzalez JA.
  9. ^ Helland IB, Smith L, Saarem K, Saugstad OD, Drevon CA. Maternal supplementation with very-long-chain n-3 fatty acids during pregnancy and lactation augments children's IQ at 4 years of age. Pediatrics. 2003 Jan;111(1):e39-44.
  10. ^ Duthie SJ, Whalley LJ, Collins AR, Leaper S, Berger K, Deary IJ. Homocysteine, B vitamin status, and cognitive function in the elderly. Am J Clin Nutr. 2002 May;75(5):908-13. Erratum in: Am J Clin Nutr. 2003 Feb;77(2):523.
  11. ^ a b Meyer, P.A., McGeehin, M.A., and Falk, H. "A global approach to childhood lead poisoning prevention," International Journal of Hygiene and Environmental Health 206, nos. 4–5 (August 2003): 363–69.
  12. ^ Low-Level Lead Exposure, Intelligence and Academic Achievement: A Long-term Follow-up Study David C. Bellinger PhD, MSc1, Karen M. Stiles PhD, MN1, and Herbert L. Needleman MD1. PEDIATRICS Vol. 90 No. 6 December 1992, pp. 855-861
  13. ^ In Utero Exposure to Background Concentrations of DDT and Cognitive Functioning among Preschoolers Núria Ribas-Fitó1, Maties Torrent2, Daniel Carrizo3, Laura Muñoz-Ortiz1, Jordi Júlvez1, Joan O. Grimalt3 and Jordi Sunyer1 American Journal of Epidemiology 2006 164(10):955-962
  14. ^ The effects of tobacco exposure on children's behavioral and cognitive functioning: implications for clinical and public health policy and future research. Weitzman M, Byrd RS, Aligne CA, Moss M. Neurotoxicol Teratol. 2002 May-Jun;24(3):397-406.
  15. ^ Maternal smoking during pregnancy and offspring IQ Naomi Breslau1,*, Nigel Paneth1, Victoria C Lucia1 and Rachel Paneth-Pollak2 International Journal of Epidemiology 2005 34(5):1047-1053
  16. ^ Exposure to Environmental Tobacco Smoke and Cognitive Abilities among U.S. Children and Adolescents Kimberly Yolton, Kim Dietrich, Peggy Auinger, Bruce P. Lanphear, and Richard Hornung1. Environ Health Perspect. 2005 January; 113(1): 98–103.
  17. ^ How similar are fluid cognition and general intelligence? A developmental neuroscience perspective on fluid cognition as an aspect of human cognitive ability, Behavioral and Brain Sciences (2006), 29: 109-125 Cambridge University Press, Clancy Blair. Multiple comments can be seen on Google Scholar.
  18. ^ Boivin, M.J., "Effects of early cerebral malaria on cognitive ability in Senegalese children," Journal of Developmental and Behavioral Pediatrics 23, no. 5 (October 2002): 353–64. Holding, P.A. and Snow, R.W., "Impact of Plasmodium falciparum malaria on performance and learning: review of the evidence," American Journal of Tropical Medicine and Hygiene 64, suppl. nos. 1–2 (January–February 2001): 68–75.
  19. ^ "Stupidity or worms": do intestinal worms impair mental performance? Watkins WE, Pollitt E. Psychol Bull. 1997 Mar;121(2):171-91
  20. ^ Naomi Breslau, PhD; Victoria C. Lucia, PhD; German F. Alvarado, MD, MPH (11, November 2006). Intelligence and Other Predisposing Factors in Exposure to Trauma and Posttraumatic Stress Disorder. A Follow-up Study at Age 17 Years. Arch Gen Psychiatry. 2006;63:1238-1245. Retrieved on August 6, 2006.
  21. ^ GT_DM_5b.pdf (PDF).
  22. ^ Effects of major depression on estimates of intelligence Sackeim HA, Freeman J, McElhiney M, Coleman E, Prudic J, Devanand DP. J Clin Exp Neuropsychol. 1992 Mar;14(2):268-88.
  23. ^ Improvement of cognitive functioning in mood disorder patients with depressive symptomatic recovery during treatment: An exploratory analysis LAURA MANDELLI, Psy. D, ALESSANDRO SERRETTI, md,1 CRISTINA COLOMBO, md, MARCELLO FLORITA, Psy. D, ALESSIA SANTORO, Psy. D, DAVID ROSSINI, MD, RAFFAELLA ZANARDI, MD AND ENRICO SMERALDI, MD. Psychiatry and Clinical Neurosciences Volume 60 Issue 5 Page 598 - October 2006
  24. ^ Whalley and Deary (2001). Longitudinal cohort study of childhood IQ and survival up to age 76. British Medical Journal 2001, 322:819-819. Retrieved on August 6, 2006.
  25. ^ Debbie A. Lawlor, University of Bristol, Heather Clark, University of Aberdeen, David A. Leon, London School of Hygiene & Tropical Medicine (2006). Associations Between Childhood Intelligence and Hospital Admissions for Unintentional Injuries in Adulthood: The Aberdeen Children of the 1950s Cohort Study. American Journal of Public Health, December 2006. Retrieved on January 10, 2007.
  26. ^ Cervilla et al (2004). Premorbid cognitive testing predicts the onset of dementia and Alzheimer's disease better than and independently of APOE genotype. Psychiatry 2004;75:1100-1106.. Retrieved on August 6, 2006.
  27. ^ Dorene Rentz, Brigham and Women's Hospital's Department of Neurology and Harvard Medical School. More Sensitive Test Norms Better Predict Who Might Develop Alzheimer's Disease. Neuropsychology, published by the American Psychological Association. Retrieved on August 6, 2006.
  28. ^ Whalley et al. (2000). Childhood mental ability and dementia. Neurology 2000;55:1455-1459.. Retrieved on August 6, 2006.
  • Sungthong, R., Mo-suwan, L., and Chongsuvivatwong, V., "Effects of haemoglobin and serum ferritin on cognitive function in school children," Asia Pacific Journal of Clinical Nutrition 11, no. 2 (2002): 117–22



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