m →Intrauterine growth retardation: rm "the" |
WeijiBaikeBianji (talk | contribs) m moved Health and intelligence to Group differences in IQ by health: Match subarticle title with title of section in main article |
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Revision as of 13:52, 8 September 2010
Health and intelligence research investigates the impact of health on intelligence. This is one of the most important factors in understanding human group differences in IQ test scores and other measures of cognitive ability. 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. Such impairment may sometimes be permanent, sometimes be partially or wholly compensated for by later growth.
Developed nations have implemented several health policies regarding nutrients and toxins known to influence cognitive function. These include laws requiring 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][2]
Improvements in nutrition, and in public policy in general, have been implicated in worldwide IQ increases (the Flynn effect).
Nutrition
Malnutrition may occur during several different periods of growth, such as pregnancy, during breastfeeding, infancy, or childhood. It may also happen due to deficiencies of different nutrients, such as micronutrients, protein or energy. This may cause different effects.
Timing
Some observers have argued that malnutrition during the first six months of life harms cognitive development much more than malnutrition later in life. However, a study from the Philippines argues that malnutrition in the second year of life may have a larger negative impact than malnutrition in the first year of life.[3]
Intrauterine growth retardation
Undernutrition during pregnancy, and other factors, may cause intrauterine growth retardation (IUGR), which is one cause of low birth weight. However, it has been suggested that in IUGR the brain may be selectively spared. Brain growth is usually less affected than whole body weight or length. Several studies from developed nations have found that with the exception of extreme intrauterine growth retardation also affecting brain growth, and hypoxic injury, IUGR seems to have little or no measurable effect on mental performance and behavior in adolescence or adulthood. For example, acute undernutrition for a few months during the Dutch famine of 1944 caused a decrease in mean birthweight in certain areas. This was later associated with a change in performance on IQ tests for 18–19 years old Dutch males draftees from these areas compared to control areas. The subjects were exposed to famine prenatally but not after birth. During the famine, births decreased more among those with lower Socioeconomic status (SES), whereas after the famine, there was a compensatory increase in births among those with lower SES. Since SES correlates with IQ, this may have hidden an effect caused by the undernutrition.[4]
Breastfeeding
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.[5] The study has been subject to various criticisms.[6] Another study found a positive effect of breastfeeding also after controlling for parental IQ.[7] Another study concluded that breastfeeding increases IQ 8.3 points on average.[2][8]
A study shows that breastmilk can raise IQ by 7 points if the infants had a "C" version of the FADS2 gene. Those with the "G" version have no IQ advantage.[9][10]
It has also been proposed that the omega3 fatty acids that are found in high doses in breast milk, and that are known to be essential constituents of brain tissues, could at least partially account for an increase in IQ.
Infancy
Two studies in Chile on 18 years old high-school graduates found that nutritional status during the first year of life affected IQ, scholastic achievement, and brain volume.[11] [12]
Micronutrients and vitamin deficiencies
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, the Copenhagen consensus, states that 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 four and under suffer from anaemia because of insufficient iron in their diets.[13]
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."[14]
Overall, studies investigating whether cognitive function in already iron-deficient children can be improved with iron supplements have produced mixed results, possibly because deficiency in critical growth periods may cause irreversible damage. However, several studies with better design have shown substantial benefits. In order to prevent iron deficiency an option is giving specific supplementation, for example as tablets. However, this is costly, distribution mechanisms are often ineffective, and compliance is low. Fortification of staple foods (cereals, flour, sugar, salt) to deliver micronutrients to children on a large scale is probably the most sustainable and affordable option, even though commitment from governments and the food industry is needed.[15] Developed nations fortify several foods with various micronutrients.[16]
Additional 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 be explained by the very large increase of 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.[17]
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.[18] Vitamin B12 and folate may be important for cognitive function in old age.[19]
Another study found that pregnant women who consumed 340 grams of low-mercury containing fish with fatty acids per week have benefits that outweigh the risks for mercury poisoning. They were less likely to have children with low verbal IQ, motor coordination and behavioral problems. However, foods containing high amounts of mercury, such as shark swordfish, king mackerel and tilefish, might cause mental retardation.[20][21][22][23][24][25]
Protein and energy malnutrition
One study from a developing country, Guatemala, found that poor growth during infancy, rather than low birth weight, was negatively related to adolescent performance on cognitive and achievement tests.[26] A later related very long term study looked at the effect of giving 6–24 months old children in Guatemala a high protein-energy drink as a dietary supplement. A significantly positive and fairly substantial effects was found on increasing the probability of attending school and of passing the first grade, increasing the grade attained by age 13, increasing completed schooling attainment, and for adults aged 25–40 increasing IQ test scores.[27]
Stunting
31% of children under the age of 5 in the developing world are moderately (height-for-age is below minus 2 standard deviations) or severely stunted (below minus 3 standard deviations).[28] The prevalence was even higher previously since the worldwide prevalence of stunting is declining by about half of a percentage point each year.[29] A study on stunted children aged 9–24 months in Jamaica found that when aged 17–18 years they had significantly poorer scores than a non-stunted group on cognitive and educational tests and psychosocial functioning. Giving a nutritional supplementation (1 kg milk based formula each week) to these already stunted children had no significant effect on later scores, but psychosocial stimulation (weekly play sessions with mother and child) had a positive effect.[30][31]
Toxins
Industrial chemicals
Certain toxins, such as lead, mercury, arsenic, toluene, and PCB are well-known causes of neuro-developmental disorders. Recognition of these risks has led to evidence-based programmes of prevention, such as elimination of lead additives in petrol. Although these prevention campaigns are highly successful, most were initiated only after substantial delays.[32]
Policies to manage lead differ between nations, particularly between the developed and developing world. 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.[33] Even slightly elevated lead levels around the age of 24 months are associated with intellectual and academic performance deficits at age 10 years.[34]
Certain, at least previously, widely used organochlorides, such as dioxins, DDT, and PCB, have been associated with cognitive deficits.[35]
A Lancet review identified 201 chemicals with the ability to cause clinical neurotoxic effects in human adults, as described in the peer-reviewed scientific literature. Most of them are commonly used. Many additional chemicals have been shown to be neurotoxic in laboratory models. The article notes that children are more vulnerable and argues that new, precautionary approaches that recognise the unique vulnerability of the developing brain are needed for testing and control of chemicals in order to avoid the previous substantial before starting restrictions on usage.[36] An appendix listed further industrial chemicals considered to be neurotoxic.[37]
Recreational drugs
Current cannabis use was found to be significantly correlated in a dose-dependent manner with a decline in IQ scores, during the effect of the use [citation needed]. However, no such decline was seen in subjects who had formerly been heavy cannabis users and had stopped taking the drug. The authors concluded that cannabis does not have a long-term effect on intelligence. Effects on fetal development are minimal when compared with the well-documented adverse effects of tobacco or alcohol use.[38]
Fetal alcohol exposure, causing Fetal alcohol syndrome, is one of the leading known causes of mental retardation in the Western world.[39]
Maternal tobacco smoking during pregnancy is associated with increased activity, decreased attention, and diminished intellectual abilities.[40] 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.[41] 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.[42]
Cosmetics
The use of some skin whitening products, unusually popular amongst Asian women,[43] has detrimental effects toward IQ. Skin whitening products often contain toxic chemicals such as mercury and hydroquinone as the active ingredient.[44][45][46] A major portion of skin whitening products, especially popular products sold in stores around Asia, have been criticized by many, such as the U.S. Food and Drug Administration, for the presence of these toxic chemicals.[47][48][49] When applied mercury and hydroquinone are absorbed through the skin into the bloodstream. Studies have shown that an increase in 100 micrograms of mercury in blood decreases IQ by an average of 14 points in children. The effects of mercury poisoning and hydroquinone poisoning, such as severe mental and physical disorders have resulted from the use of mercury-containing and hydroquinone-containing cosmetic products, including skin-whitening products.[50][51][52][53] The use of skin whitening products is especially popular in Hong Kong.[54] However, a majority of products sold there are cited by Hong Kong officials to contain mercury as its active ingredient, often 27,000 to 60,000 times the "acceptable" dose.[54] Skin whitening products containing mercury or hydroquinone are also very harmful to the brain development of fetuses in pregnant women.[55][56][57][58][59]
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]
Stress
A recent theory suggests that early childhood stress may affect the developing brain and cause negative effects.[60] Exposure to violence in childhood has been associated with lower school grades[61] and lower IQ in children of all races.[62] A group of largely African American urban first-grade children and their caregivers were evaluated using self-report, interview, and standardized tests, including IQ tests. The study reported that exposure to violence and trauma-related distress in young children were associated with substantial decrements in IQ and reading achievement. Exposure to Violence or Trauma lead to a 7.5-point (SD, 0.5) decrement in IQ and a 9.8-point (SD, 0.66) decrement in reading achievement.[61] Violence may have a negative impact on IQ, or IQ may be protective against violence.[62] The causal mechanism and direction of causation is unknown.[61] Neighborhood risk has been related to lower school grades for African-American adolescents in another study from 2006.[63] Violence may also be more prevalent in the homes of parents with lower IQ's. These parents could have genetically produced children with lower IQ's.
Infectious diseases
A 2010 study by Eppig, Fincher and Thornhill found a close correlation between the infectious disease burden in a country and the average IQ of its population. The researchers found that when disease was controlled for, IQ showed no correlation with other variables such as educational and nutritional levels. Since brain development requires a very high proportion of all the body's energy in newborns and children, the researchers argue that fighting infection reduces children's IQ potential. The Eppig research may help to explain the Flynn effect, the rise in intelligence noted in rich countries.[64]
Tropical infectious diseases
Malaria affects 300–500 million persons each year, mostly children under age five 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.[65] 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.
Roundworms infect hundreds of millions of people. There is evidence that high intensities of worms in the intestines can affect mental performance.[66]
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. Many diseases may be neurological or psychiatric and may primarily affect the brain. Others may affect many other organs, like HIV, Hashimoto's thyroiditis causing hypothyroidism, or cancer.
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.[citation needed] 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.[67] On the other hand, higher IQ shows a higher prevalence of those conditioned with Obsessive Compulsive Disorder.[68]
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.[69][70]
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.[71] 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.[72]
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.[73]
However, when diagnosing individuals with a higher level of cognitive ability, in this study those with IQ's of 120 or more,[74] 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.[75]
See also
References
- ^ a b Olness K (2003). "Effects on brain development leading to cognitive impairment: a worldwide epidemic". J Dev Behav Pediatr. 24 (2): 120–30. PMID 12692458.
{{cite journal}}
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ignored (help) - ^ a b Perlmutter, David (2006). Raise a Smarter Child By Kindergarten: Raise Iq Points By Up to 30 Points and Turn on Your Child's Smart Genes Points. Morgan Road Books. ISBN 978-0767923019.
{{cite book}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - ^ Glewwe P, King EM (2001). "The Impact of Early Childhood Nutritional Status on Cognitive Development: Does the Timing of Malnutrition Matter?". World Bank Economic Review. 15 (1): 81–113. doi:10.1093/wber/15.1.81.
- ^ "Causes and consequences of intrauterine growth retardation. Proceedings of an IDECG Workshop. Baton Rouge, Louisiana, USA. November 11-15, 1996" ([dead link]). Eur J Clin Nutr. 52 (Suppl 1): S1–103. 1998. PMID 9547065.
{{cite journal}}
: Unknown parameter|month=
ignored (help) Neisser; et al. (August 7, 1995). "Intelligence: Knowns and Unknowns". Board of Scientific Affairs of the American Psychological Association. Retrieved August 6, 2006.{{cite web}}
: Explicit use of et al. in:|author=
(help) - ^
Der G, Batty GD, Deary IJ (2006). "Effect of breast feeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis". BMJ. 333 (7575): 945. doi:10.1136/bmj.38978.699583.55. PMC 1633819. PMID 17020911.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Rapid Responses
- ^ Gómez-Sanchiz M, Cañete R, Rodero I, Baeza JE, González JA (2004). "Influence of breast-feeding and parental intelligence on cognitive development in the 24-month-old child". Clin Pediatr (Phila). 43 (8): 753–61. doi:10.1177/000992280404300811. PMID 15494884.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Masters R (1997). "Brain biochemistry and social status: The neurotoxicity hypothesis". In White, Elliott (ed.). Intelligence, political inequality, and public policy. New York, N.Y: Prager. pp. 141–183. ISBN 0-275-95655-5.
- ^ Baby's IQ Raised by Breastmilk and Genes
- ^ Caspi A, Williams B, Kim-Cohen J; et al. (2007). "Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism". Proceedings of the National Academy of Sciences. 104 (47): 18860. doi:10.1073/pnas.0704292104. PMC 2141867. PMID 17984066.
{{cite journal}}
: Explicit use of et al. in:|author=
(help)CS1 maint: multiple names: authors list (link) - ^ Ivanovic DM, Leiva BP, Pérez HT; et al. (2002). "Nutritional status, brain development and scholastic achievement of Chilean high-school graduates from high and low intellectual quotient and socio-economic status". Br. J. Nutr. 87 (1): 81–92. doi:10.1079/BJN2001485. PMID 11895316.
{{cite journal}}
: Explicit use of et al. in:|author=
(help); Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Ivanovic DM, Leiva BP, Pérez HT; et al. (2004). "Head size and intelligence, learning, nutritional status and brain development. Head, IQ, learning, nutrition and brain". Neuropsychologia. 42 (8): 1118–31. doi:10.1016/j.neuropsychologia.2003.11.022. PMID 15093150.
{{cite journal}}
: Explicit use of et al. in:|author=
(help)CS1 maint: multiple names: authors list (link) - ^ Behrman, J.R., Alderman, H., and Hoddinott, J., "Hunger and Malnutrition," Copenhagen Consensus 2004.
- ^ UNICEF and The Micronutrient Initiative, "Vitamin & Mineral Deficiency: A Global Progress Report," March 2004.
- ^ Saloojee H, Pettifor JM (2001). "Iron deficiency and impaired child development". BMJ. 323 (7326): 1377–8. doi:10.1136/bmj.323.7326.1377. PMC 1121846. PMID 11744547.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - ^ FOOD FORTIFICATION TECHNOLOGY Food Fortification: Technology and Quality Control. (FAO Food And Nutrition Paper - 60)
- ^ Schoenthaler SJ, Bier ID, Young K, Nichols D, Jansenns S (2000). "The effect of vitamin-mineral supplementation on the intelligence of American schoolchildren: a randomized, double-blind placebo-controlled trial". J Altern Complement Med. 6 (1): 19–29. doi:10.1089/acm.2000.6.19. PMID 10706232.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Helland IB, Smith L, Saarem K, Saugstad OD, Drevon CA (2003). "Maternal supplementation with very-long-chain n-3 fatty acids during pregnancy and lactation augments children's IQ at 4 years of age". Pediatrics. 111 (1): e39–44. doi:10.1542/peds.111.1.e39. PMID 12509593.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Duthie SJ, Whalley LJ, Collins AR, Leaper S, Berger K, Deary IJ (2002). "Homocysteine, B vitamin status, and cognitive function in the elderly". Am. J. Clin. Nutr. 75 (5): 908–13. PMID 11976166.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) Erratum in: Am. J. Clin. Nutr. 77 (2): 523. 2003.{{cite journal}}
: Missing or empty|title=
(help); Unknown parameter|month=
ignored (help) - ^ Lyketsos CG (2003). "Should pregnant women avoid eating fish? Lessons from the Seychelles". Lancet. 361 (9370): 1667–8. doi:10.1016/S0140-6736(03)13379-X. PMID 12767728.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - ^ Pregnant Women: Eat More Fish or Not? - To Your Health - MSNBC.com
- ^ Fish Diet in Pregnancy May Hone Kids' IQ
- ^ Diet and the unborn child | The omega point | Economist.com
- ^ Medical News: Eating Fish During Pregnancy Provides 'Brain Food' for Child - in OB/GYN, Pregnancy from MedPage Today
- ^ Pregnant? Omega-3 Essential for Baby's Brain
- ^ Pollitt E, Gorman KS, Engle PL, Martorell R, Rivera J (1993). "Early supplementary feeding and cognition: effects over two decades". Monogr Soc Res Child Dev. 58 (7). Monographs of the Society for Research in Child Development, Vol. 58, No. 7: 1–99, discussion 111–8. doi:10.2307/1166162. PMID 8272081.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Stein AD, Behrman JR, DiGirolamo A; et al. (2005). "Schooling, educational achievement, and cognitive functioning among young Guatemalan adults". Food Nutr Bull. 26 (2 Suppl 1): S46–54. PMID 16060211.
{{cite journal}}
: Explicit use of et al. in:|author=
(help); Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Children's Health: Stunting in children under 5-moderate and severe
- ^ Stunted growth affects almost 40 percent of the developing world's infants, Cornell study reports
- ^ Effects of early childhood psychosocial stimulation and nutritional supplementation on cognition and education in growth-stunted Jamaican children: prospective cohort study Lancet (British edition), 2005 (Vol. 966) (No. 9499) 1804-1807. Walker, S. P., Chang, S. M., Powell, C. A., Grantham-McGregor, S. M.
- ^ Walker SP, Chang SM, Powell CA, Simonoff E, Grantham-McGregor SM (2006). "Effects of psychosocial stimulation and dietary supplementation in early childhood on psychosocial functioning in late adolescence: follow-up of randomised controlled trial". BMJ. 333 (7566): 472. doi:10.1136/bmj.38897.555208.2F. PMC 1557928. PMID 16877454.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Grandjean P, Landrigan PJ (2006). "Developmental neurotoxicity of industrial chemicals". Lancet. 368 (9553): 2167–78. doi:10.1016/S0140-6736(06)69665-7. PMID 17174709.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - ^ Meyer PA, McGeehin MA, Falk H (2003). "A global approach to childhood lead poisoning prevention". Int J Hyg Environ Health. 206 (4–5): 363–9. doi:10.1078/1438-4639-00232. PMID 12971691.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Bellinger DC, Stiles KM, Needleman HL (1992). "Low-level lead exposure, intelligence and academic achievement: a long-term follow-up study". Pediatrics. 90 (6): 855–61. PMID 1437425.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Ribas-Fitó N, Torrent M, Carrizo D; et al. (2006). "In utero exposure to background concentrations of DDT and cognitive functioning among preschoolers". Am. J. Epidemiol. 164 (10): 955–62. doi:10.1093/aje/kwj299. PMID 16968864.
{{cite journal}}
: Explicit use of et al. in:|author=
(help); Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Grandjean P, Landrigan PJ (2006). "Developmental neurotoxicity of industrial chemicals". Lancet. 368 (9553): 2167–78. doi:10.1016/S0140-6736(06)69665-7. PMID 17174709.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - ^ Potentials for exposure to industrial chemicals suspected of causing developmental neurotoxicity Philippe Grandjean, MD, PhD, Adjunct Professor Marian Perez, MPH, Project Coordinator Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA
- ^ Iversen L (2005). "Long-term effects of exposure to cannabis". Curr Opin Pharmacol. 5 (1): 69–72. doi:10.1016/j.coph.2004.08.010. PMID 15661628.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - ^ Abel EL, Sokol RJ (1987). "Incidence of fetal alcohol syndrome and economic impact of FAS-related anomalies". Drug Alcohol Depend. 19 (1): 51–70. doi:10.1016/0376-8716(87)90087-1. PMID 3545731.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - ^ Weitzman M, Byrd RS, Aligne CA, Moss M (2002). "The effects of tobacco exposure on children's behavioral and cognitive functioning: implications for clinical and public health policy and future research". Neurotoxicol Teratol. 24 (3): 397–406. doi:10.1016/S0892-0362(02)00201-5. PMID 12009494.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Breslau N, Paneth N, Lucia VC, Paneth-Pollak R (2005). "Maternal smoking during pregnancy and offspring IQ". Int J Epidemiol. 34 (5): 1047–53. doi:10.1093/ije/dyi163. PMID 16085682.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Yolton K, Dietrich K, Auinger P, Lanphear BP, Hornung R (2005). "Exposure to environmental tobacco smoke and cognitive abilities among U.S. children and adolescents". Environ. Health Perspect. 113 (1): 98–103. doi:10.1289/ehp.7210. PMC 1253717. PMID 15626655.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ In a survey, 28% of Koreans and 50% of Philippians say that they use skin whitening products. "Skin lightening in Asia? A bright future?".
- ^ Counter, S. Allen (December 16, 2003). Whitening skin can be deadly. The Boston Globe.
- ^ Heyward, Georgia (February 5, 2005). New York City Warns: Some Skin Creams Are Poisonous. The Epoch Times.
- ^ "Mercury in Cosmetic Skin Whitening Creams" ([dead link] – Scholar search).
{{cite web}}
: External link in
(help)|format=
- ^ "FDA Proposes Hydroquinone Ban". FDA bans hydroquinone in skin whitening products
- ^ "Skin-lightening creams face FDA ban: Dermatologists defend treatment" ([dead link] – Scholar search).
{{cite web}}
: External link in
(help) FDA bans hydroquinone in skin whitening products|format=
- ^ "NYC HEALTH DEPT. WARNS AGAINST USE OF "SKIN-LIGHTENING" CREAMS CONTAINING MERCURY OR SIMILAR PRODUCTS WHICH DO NOT LIST INGREDIENTS". January 27, 2005.
- ^ "Skin Lightening". Article that links skin whitening products to mercury and hydroquinone
- ^ Countera, S. Allen. "Mercury exposure in children: a review" (PDF).
{{cite journal}}
: Cite journal requires|journal=
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ignored (|author=
suggested) (help) - ^ Clarkson. "The Toxicology of Mercury and Its Chemical Compounds" ([dead link] – Scholar search).
{{cite journal}}
: Cite journal requires|journal=
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|coauthors=
ignored (|author=
suggested) (help) - ^ Mahaffey, Kathryn R. "Dynamics of Mercury Pollution on Regional and Global Scales".
- ^ a b Bray, Marianne (May 15, 2002). SKIN DEEP: Dying to be white. CNN. Retrieved May 4, 2010.
- ^ "Asian Skin Tanning Article". An argument that links skin whitening products to the development of the brain of a fetus of pregnant Asian women, both mercury and hydroquinone. Therefore it is not WP:SYN
- ^ "Mercury Fact Sheet" ([dead link] – Scholar search).
{{cite web}}
: External link in
(help) Another argument that links skin whitening products to the development of the brain of a fetus of pregnant Asian women. Therefore it is not WP:SYN|format=
- ^ "DOES LOW MERCURY CONTAINING IN-LIGHTENING CREAM (FAIR & LOVELY) EFFECT THE KIDNEY, LIVER, AND BRAIN OF FEMALE MICE?". Another argument that links skin whitening products to the development of the brain of a fetus of pregnant Asian women, both mercury and hydroquinone. Therefore it is not WP:SYN
- ^ Yang MG, Krawford KS, Garcia JD, Wang JH, Lei KY (1972). "Deposition of mercury in fetal and maternal brain". Proc. Soc. Exp. Biol. Med. 141 (3): 1004–7. PMID 4645746.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Shafiq-ur-Rehman, Rehman S, Chandra O, Abdulla M (1995). "Evaluation of malondialdehyde as an index of lead damage in rat brain homogenates". Biometals. 8 (4): 275–9. doi:10.1007/BF00141599. PMID 7580048.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Blair C (2006). "How similar are fluid cognition and general intelligence? A developmental neuroscience perspective on fluid cognition as an aspect of human cognitive ability". Behav Brain Sci. 29 (2): 109–25, discussion 125–60. doi:10.1017/S0140525X06009034. PMID 16606477.
{{cite journal}}
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ignored (help) Multiple comments can be seen on Google Scholar. - ^ a b c Delaney-Black V, Covington C, Ondersma SJ; et al. (2002). "Violence exposure, trauma, and IQ and/or reading deficits among urban children". Arch Pediatr Adolesc Med. 156 (3): 280–5. doi:10.1001/archpedi.156.3.280. PMID 11876674.
{{cite journal}}
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ a b Saltzman KM, Weems CF, Carrion VG (2006). "IQ and posttraumatic stress symptoms in children exposed to interpersonal violence". Child Psychiatry Hum Dev. 36 (3): 261–72. doi:10.1007/s10578-005-0002-5. PMID 16362242.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Gonzales NA, Cauce AM, Friedman RJ, Mason CA (1996). "Family, peer, and neighborhood influences on academic achievement among African-American adolescents: one-year prospective effects". Am J Community Psychol. 24 (3): 365–87. doi:10.1007/BF02512027. PMID 8864209.
{{cite journal}}
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ MacKenzie, Debora. "Link found between infectious disease and IQ". New Scientist. Retrieved 4 July 2010.
- ^ Boivin MJ (2002). "Effects of early cerebral malaria on cognitive ability in Senegalese children". J Dev Behav Pediatr. 23 (5): 353–64. PMID 12394524.
{{cite journal}}
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ignored (help) - ^ Watkins WE, Pollitt E (1997). ""Stupidity or worms": do intestinal worms impair mental performance?". Psychol Bull. 121 (2): 171–91. doi:10.1037/0033-2909.121.2.171. PMID 9100486.
{{cite journal}}
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ignored (help) - ^ Breslau N, Lucia VC, Alvarado GF (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. 63 (11): 1238–45. doi:10.1001/archpsyc.63.11.1238. PMID 17088504.
{{cite journal}}
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ "GT_DM_5b.pdf" (PDF).
- ^ Sackeim HA, Freeman J, McElhiney M, Coleman E, Prudic J, Devanand DP (1992). "Effects of major depression on estimates of intelligence". J Clin Exp Neuropsychol. 14 (2): 268–88. doi:10.1080/01688639208402828. PMID 1572949.
{{cite journal}}
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Mandelli L, Serretti A, Colombo C; et al. (2006). "Improvement of cognitive functioning in mood disorder patients with depressive symptomatic recovery during treatment: an exploratory analysis". Psychiatry Clin. Neurosci. 60 (5): 598–604. doi:10.1111/j.1440-1819.2006.01564.x. PMID 16958944.
{{cite journal}}
: Explicit use of et al. in:|author=
(help); Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Whalley LJ, Deary IJ (2001). "Longitudinal cohort study of childhood IQ and survival up to age 76". BMJ. 322 (7290): 819. doi:10.1136/bmj.322.7290.819. PMC 30556. PMID 11290633.
{{cite journal}}
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ignored (help) - ^ Lawlor DA, Clark H, Leon DA (2007). "Associations between childhood intelligence and hospital admissions for unintentional injuries in adulthood: the Aberdeen Children of the 1950s cohort study". Am J Public Health. 97 (2): 291–7. doi:10.2105/AJPH.2005.080168. PMC 1781410. PMID 17194859.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Cervilla J, Prince M, Joels S, Lovestone S, Mann A (2004). "Premorbid cognitive testing predicts the onset of dementia and Alzheimer's disease better than and independently of APOE genotype". J. Neurol. Neurosurg. Psychiatr. 75 (8): 1100–6. doi:10.1136/jnnp.2003.028076. PMC 1739178. PMID 15258208.
{{cite journal}}
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ 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 August 6, 2006.
- ^ Whalley LJ, Starr JM, Athawes R, Hunter D, Pattie A, Deary IJ (2000). "Childhood mental ability and dementia". Neurology. 55 (10): 1455–9. PMID 11094097.
{{cite journal}}
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