Are we hurting our noggins? Internationally, are there social customs, diseases, pollutants, school policies, parental choices, drugs, diets and philosophies that cause, or are correlated with, decreased intelligence? Here are fourscore-and-a-trio of the mind-mangling menaces. A preponderance of the fearsome factors have undergone scientific scrutiny, with statistics filed in the massive archives of pubmed.gov.
prenatal - damaged before you’re delivered
Cousin Marriages – “Consanguineous” marriages between cousins or relatives more than triples the rate of mental retardation. One study shows an average IQ drop of 7 points; another reveals a loss of 11.2 points.
Avoiding PreNatal Diagnosis - Fetal Screening can determine if fetuses have birth defects or genetic diseases that cause cognitive damage. Recommended for older parents and those carrying genes of genetic disorders.
Prenatal Iodine Deficiency – The World Health Organization says iodine deficiency is the “single greatest preventable cause of mental retardation.” Average deduction is 10-17 IQ points.
Prenatal Folic Acid Deficiency - Infants with neural tube defects suffer a loss of 15 IQ points.
Prenatal Choline Deficiency – Can wreck spatial memory and hippocampal plasticity in adulthood.
Fetal Alcohol Syndrome (Heavy Alcohol Exposure) - Children afflicted with fetal alcohol syndrome have an average IQ of 75.
Moderate Prenatal Alcohol Exposure - Gestating women who imbibe two alcoholic drinks per day hamper their child’s IQ with a 7-point loss.
Pesticide Exposure - Prenatal (and postnatal) exposure to organophosphate pesticides can cause a deficit of 7.0 IQ points.
Prenatal Cigarette Exposure - Loss of IQ is reported as 3.3, 6.2, and 15 points in various studies.
Prenatal Hydrocarbons (Smog) Exposure - Two studies showed IQ losses of 4.31 and 3.8 points.
Prenatal Cocaine Exposure - Boys exposed to cocaine had lower IQs at 4, 6, and 9 years of age.
Prenatal Methamphetamine Exposure – Meth exposure leads to weakened verbal memory, and damage to visual motor integration, attention, and long-term spatial memory.
Embryonic Malnutrition - Multiple infants sharing a womb are at risk of suboptimal nutrition. Lighter twins have verbal IQ that’s 7.5 points lower than heavier twins.
Maternal Stress – Children exposed to high cortisol levels in the womb, caused by maternal stress, suffer an average verbal IQ loss of 3.83 points.
Prenatal Valproate Exposure - Embryos exposed to Valproate have IQ scores up to 9 points lower than children exposed to other anti-epileptic medications.
Prenatal Excess Mercury Exposure - Reports vary, but one study concluded that excessive prenatal intake of mercury in fish costs children 1.5 points in IQ.
Prenatal Radiation Exposure –Embryos exposed to radiation had more speech-language disorders, emotional disorders, and borderline IQ.
Premature Birth - Babies delivered before 40 weeks have smaller heads and an IQ 4.9 points lower than infants delivered after 40+ weeks.
Breech Birth - Males born via breech birth have a 7-point lower IQ than boys who were born in cephalic presentation.
early years – not breastfed? tragic, but there are factors more horrible
Malaria - The brain insult of cerebral malaria leaves victims with brain impairment in planning, decision-making, self-awareness, and social sensitivity.
Diarrhea – Diarrheal diseases in the first five years can cause detrimental brain development and lower IQ.
Tuberculosis - Tuberculosis Meningitis potentially causes brain damage. TB’s toll on the immune system also retards children’s cognitive development.
Intestinal Worms - Intestinal worms can reduce IQ; one estimate is a loss of 3.75 points per worm infection.
Iodine Deficiency - Children who do not receive sufficient quantities of the 53rd element can suffer a 10-15 point IQ drop.
Iron Deficiency - Anemic children are at risk of losing 5-10+ IQ points.
Zinc Deficiency - Children aged 6-11 with zinc deficiency suffer damage to their memory system.
Severe Malnutrition – Malnourished children at the age of 3 have a 15.3 IQ deficit at the age of 11.
Lead Poisoning – Studies report a 4-9 point decrease in IQ in children who are over-exposed to lead.
Manganese Poisoning – High exposure to the 25th element leads to a 2.4 point IQ loss in children.
Phenobarbital Usage - Children treated for febrile seizures with phenobarbital had IQs reduced by 3.71 points.
Fluoride Poisoning - 6-10 year-old children with excessive fluoride in their drinking water experience a 10.2 point IQ drop.
Indoor Mold – Young children living in mold-contaminated homes triple the risk of low IQ scoring.
Unhealthy Diet – Children who eat a poor diet (high fat and sugar) have an IQ 5 points lower than those with a health-conscious diet (salad, rice, pasta, fish, fruit).
Shaken Baby Syndrome (SBS) – The physical abuse causes traumatic brain injury with damage to IQ, working memory, and mental organization.
Trauma and Spankings- Violence puts a traumatic burden on children that leads to a 7.5-point decrement in IQ.
Harsh Corporal Punishment – People exposed to HCP for a minimum of 3 years suffer a reduction in their brain’s gray matter volume.
Parental Verbal Abuse – The brain’s white matter is reduced in children who experience maternal verbal abuse, in three areas. Verbal IQ is reduced.
Witnessing Domestic Violence - Children exposed to high levels of domestic violence have IQs that are 8 points lower.
Child Sexual Abuse - Children subjected to sexual abuse suffer long-term deficits in verbal short-term memory.
Female Genital Mutilation - The World Health Organization (WHO) asserts that FGM poses a “mental health risk.”
Maternal Depression – Children of women who were depressed at three months postpartum have significantly lower IQ scores. (this is remedied when the mother recovers.)
Mother’s Education – Children whose mothers are high school dropouts have an average IQ of 93, fifteen points lower than children whose mothers finished college.
Teen Mothers – Children whose mothers were younger than 19 when they were born are born with smaller heads and have average IQ scores of 96, five points less than children born from mothers in their late twenties.
Unmarried Mothers – Children with never-wed mothers have IQ scores of 94, those with father absent score 99, and those with both parents at home score 100.
Family Poverty - Children from families below the poverty line have average IQs of 93 - children in the highest income bracket have average IQs of 106.
Cognitive-Damaging Cartoon – Watching “SpongeBob SquarePants” for nine minutes impairs 4-year-old’s executive function.
Limit “Screen Time” – Early television over-exposure can damage young children’s neurological systems, resulting in hyperactivity and abbreviated attention spans.
Breast-feeding – Studies report a 2-7 point IQ gap in children who don’t receive breast milk.
Maternal Bonding - 4 year-olds who don’t have a close relationship with their mother have a lower IQ.
Lack of Emotional Support – Parental lack of emotional support is associated with a 5-point disadvantage in child’s IQ.
Big Families - Children from families with five or more children have an average IQ of 92, from a four-child family the IQ is 97, with a one-child family scoring 104.
Psychosocial and Cognitive Stimulation – Children with the lowest cognitive stimulation have IQs 12 points lower than children with the highest.
Didn’t Go To Preschool? - A study in India demonstrates that children aged 4-6 advanced 10.2 IQ points if they were placed in preschool education programs.
National Poverty – In high-income countries only 3-5 children per 1,000 have severe intellectual disability, in developing nations the rate can be 22 per 1,000.
school years - not all educations are equals, and teens take cognitive risks
Lack of Exercise – Ten-year-olds who are out-of-shape perform worse on cognitive tests then their physically-fit peers. The hippocampus and dentate gyrus are smaller.
Teen Obesity – Studies correlate low IQ and teen obesity; average IQ of subjects was about 85.
Bulimia – Bulimia nervosa can negatively affect brain regions involved in the reward circuitry.
Anorexia – Anorexia nervosa may shrink the afflicted person’s brain matter.
Junk Food – Young children fed junk food develop IQs up to five points lower than healthy eaters, because they consume insufficient vitamins and minerals for optimal brain growth.
Artificial Additives - In Pakistani, students who ate a meal before IQ testing that did not contain artificial flavors, preservatives and colors, had IQ test scores 14 percent higher than individuals who consumed food with additives.
Big Classrooms – Large classrooms disadvantage children. Small classrooms are superior. Deduct two IQ points per year.
School Drop Outs - Students with lesser amounts of schooling lost an average of 2-3 IQ points per year missed.
Bad Teachers - The negative impact is approximately two IQ points per year.
Concussions - 300,000 concussions occur annually in the USA in teen football programs. Loss of IQ can occur after a single concussion.
Alcohol - Children and teenagers who drink alcohol expose their still-developing cognition to possible long-term mental impairment.
Marijuana - Kids who use marijuana before the age of 16 can develop problems in making decisions, cognitive flexibility, and recalling details.
Smoking – Regular smoking during early adulthood is associated with cognitive impairments.
Second-Hand Tobacco Smoke Exposure - 6-16 year olds exposed to second-hand tobacco smoke can suffer a decrease of 5.0 points in IQ reading scores.
Watching Online Violence - When kids play a variety of violent video games the amygdala is aroused, leading to aggressive, impulsive behavior.
adults – finally you’re grown up… now your brain starts to decline…
Adult Obesity – Obesity causes a decline in the brain’s cognitive abilities, particularly in learning and memory.
Adult Marijuana Use - Evidence suggests impaired neurological functioning in long-term or heavy cannabis users, including damage to encoding, storage, manipulation, and retrieval.
Khat – The East Africa drug impairs cognitive flexibility and updating of information in working memory.
Head Injury - Adults who incur whiplash with head impact in a car accident had a 14-point IQ loss after 20 weeks.
Summer Stupor - Lazy, sunbathing vacations can wither IQ by 20 points. Inactivity and dehydration reduce oxygen to the brain, dim neurons, and shrink frontal lobes. Situation reverses when weather changes and work resumes.
Chronic traumatic stress – Elevated levels of cortisol are associated with cognitive decrements, with deleterious effects on verbal, learning, delayed recall and visual-spatial abilities.
Obsessively Checking Electronic Messages – Employees who obsessively check their phone calls, emails and text messages throughout the day suffer an IQ drop of 10 points.
Adult Smoking – Heavy cigarette smoking is associated with earlier onset of Alzheimer’s disease by 2-3 years.
Cold Weather - Researchers at California School of Professional Psychology claim that “persons in colder climates tend to have higher IQs.” The theory correlates with data from the 50 United States.
Religious Fundamentalism – A 2010 survey reported that adults who identified themselves as “very religious” had an average 97.14 IQ, while those self-described as “not at all religious” had an average IQ of 103.09.
Political Conservatism – A survey reports that people who categorize themselves as “very conservative” had average IQ of 95 during teen years. People self-described as “very liberal” have an IQ of 106.
Amnesia - Multiple types of this disorder destroy memory functions. Generally it is related to bilateral hippocampal pathology.
Hypoxia - Depriving the body - and subsequently the brain - of oxygen. Brain regions that are asphyxiated the most suffer the greatest debilitation. Often caused by shock, stroke, and heart attacks.
Chemotherapy - The cancer treatment can cause temporary attention weakness, short-term memory loss, and other debilitations to cognition. Nickname for the side effect is “chemobrain.”
Feeling sub-optimal yet? Personally, I was the “small twin” in family of nine, my elementary classrooms had 45-50 students, I wasn’t breastfed, and I probably had worms. Nobody can completely escape mental harm.
That long list of 84 above; what did I miss? Please, if you have additional data that estimates the idiotic effects of anything else, like sniffing airplane glue or enduring a fraternity initiation, place your info in the comment section below.
Hank Pellissier was IEET’s Managing Director on January-October in 2012, and an IEET Affiliate Scholar. He’s the author of two e-books, Invent Utopia Now and Why is the IQ of Ashkenazi Jews so High? He is currently at BrighterBrains.org
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