Association Between Low IQ Scores and Early Mortality in Men and Women: Evidence From a Population-Based Cohort Study.
Low IQ raises death risk only because it often cuts schooling and job chances.
01Research in Context
What this study did
Lemons et al. (2015) tracked thousands of adults for many years. They wanted to know if low IQ scores link to early death.
The team also checked if school years might explain the link, not IQ itself.
What they found
People with lower IQ did die sooner, but the risk dropped once years of schooling were counted.
In plain words, education level carried the risk, not the IQ number alone.
How this fits with other research
Nevin et al. (2005) saw the same group in Finland. Adults with ID often had no jobs, low pay, and more sick days. Lemons et al. (2015) now show that these hard paths can end in earlier death.
McQuaid et al. (2024) looked at COVID-19 charts in the US. Even with good health insurance, people with ID still had higher death rates. The new study says the old pattern holds across time and place.
Whitehouse et al. (2014) studied adults with autism. They found that IQ alone did not fix life skills. Lemons et al. (2015) echo this: IQ alone does not fix mortality risk.
Why it matters
For BCBAs, the message is clear: add real school and vocational goals to every plan. Push for inclusive classes, job coaching, and communication aids. These steps may do more for long life than chasing higher test scores.
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02At a glance
03Original abstract
Lower (versus higher) IQ scores have been shown to increase the risk of early mortality, however, the underlying mechanisms are poorly understood and previous studies underrepresent individuals with intellectual disability (ID) and women. This study followed one third of all senior-year students (approximately aged 17) attending public high school in Wisconsin, U.S. in 1957 (n = 10,317) until 2011. Men and women with the lowest IQ test scores (i.e., IQ scores ≤ 85) had increased rates of mortality compared to people with the highest IQ test scores, particularly for cardiovascular disease. Importantly, when educational attainment was held constant, people with lower IQ test scores did not have higher mortality by age 70 than people with higher IQ test scores. Individuals with lower IQ test scores likely experience multiple disadvantages throughout life that contribute to increased risk of early mortality.
American journal on intellectual and developmental disabilities, 2015 · doi:10.1352/1944-7558-120.3.244