The Effects of Abuse on Intelligence
There’s not a lot we can do about the intelligence we have inherited from our parents. It’s a part of nature that we are given the genes that will bring us musical talent or inability to focus our attention, high intelligence or severe dyslexia (or both), nearsightedness, separated ear lobes, or migraines. What happens after we are conceived can make a huge difference, however, starting with prenatal nutrition or exposures. Postnatal factors such as breastfeeding, environmental toxins, and abuse can significantly alter intelligence. In fact,
Nearly all personality traits show that, contrary to expectations, environmental effects actually cause adoptive siblings raised in the same family to be as different as children raised in different families (1)
Any parent can tell you that his children are as different as night and day. What has recently come to light is the study of the effects of abuse. In one study,
Deficits in verbal declarative memory as measured by specific subtests of the WMS-R were found in women with abuse and PTSD relative to women with abuse without PTSD, and nonabused women without PTSD. These deficits were specific to verbal declarative memory. Findings were significant after controlling for years of education, history of alcohol abuse, and differences in IQ. Increased PTSD symptoms and increased severity of abuse correlated with deficits in verbal declarative memory as measured by the subtests of the WMS-R. (2)
Declarative memory is the ability to verbally recount events that have happened in the past.
Another study reports
Adolescents and young adults with a history of childhood maltreatment were 3 times more likely to become depressed or suicidal compared with individuals without such a history (p < .01). Adverse contextual factors, including family environment, parent and child characteristics, accounted for much of the increased risk for depressive disorders and suicide attempts in adolescence but not in adulthood (p < .01). The effects of childhood sexual abuse were largest and most independent of associated factors. Risk of repeated suicide attempts was 8 times greater for youths with a sexual abuse history (odds ratio = 8.40, p < .01). (3)
The 298 adolescents (7.9 percent) who had been reported as victims of maltreatment scored the equivalent of approximately three IQ points lower than those who had not been maltreated, after accounting for a large range of socioeconomic and other factors. (4)
Children exposed to violence towards either themselves or their parent during the first two years of life were shown to have a seven-point difference in cognitive skills by age eight. The families involved were also low socio-economic status, so their home environment may have also played a role by lacking stimulation. The average impairment due to lead contamination is only six points. (5)
Studies of abuse have been developing for thirty years or more, but it is hard to pinpoint the damage that is done because it frequently occurs within settings composed of multiple damaging factors. In addition, the definition of abuse is very elusive. However, if you know of an incidence of abuse in a relative or friend, you have an obligation to that child to speak up. Speak to a counselor, get some help for the family if you can. The world will be better for it.
(1) Artmann, Robert. IQ Test. No supporting information. https://www.iq-tests.eu/iq-test-Environment-410.html, accessed 5/10/17, 5/23/17.
(2) J. Douglas Bremner, MD, Eric Vermetten, MD, Nadeem Afzal, MD, and Meena Vythilingam, MD. “Deficits in Verbal Declarative Memory Function in Women With Childhood Sexual Abuse-Related Posttraumatic Stress Disorder”. https://www.researchgate.net/profile/Eric_Vermetten/publication/8258620_Deficits_in_Verbal_Declarative_Memory_Function_in_Women_With_Childhood_Sexual_Abuse-Related_Posttraumatic_Stress_Disorder/links/0fcfd507333c273a1a000000.pdf
(3) BROWN, JOCELYN M.D., M.P.H.; COHEN, PATRICIA Ph.D.; JOHNSON, JEFFREY G. Ph.D.; SMAILES, ELIZABETH M. M.Phil. “Childhood Abuse and Neglect: Specificity of Effects on Adolescent and Young Adult Depression and Suicidality”. Copyright 1999 © American Academy of Child and Adolescent Psychiatry. http://www.facmed.unam.mx/cainm/publicaciones/biblio/23.html, accessed 5/23/17.
(4) Dr. Ryan Mills, Dr Strathearn or Penny Robinson. “Children who were abused or neglected have lower IQ in teens” University of Queens, UQ Communications. 22 December 2010. Accessed 5/23/17.
(5) Ehrman, Jan. “Experiencing, Observing Abuse Is Linked to Lower Childhood IQ,” NIH Record, Vol. LXIV, No. 13. June 22, 2012. https://nihrecord.nih.gov/newsletters/2012/06_22_2012/story4.htm. Accessed 5/23/17.