Cognitive Abilities and Educational Attainment as Antecedents of Mental Disorders: A Total Population Study of Males

IQ Research
1

A new article investigates the relationship between IQ (at ages 17-18) and mental health diagnoses (at ages 36-40) in >95% of Norwegian men. The results show how powerful IQ is as a predictor for later life outcomes.

Article 1
Article 1892×844 170 KB

19.38% of men were diagnosed with at least one mental disorder by midlife, with depression being the most common (9.05%). For all disorders–with the exception of bipolar disorder and mania (labeled as “affective psychosis” in the graph below), a diagnosis was most common in the lowest IQ group and least common in the highest IQ group.

Article 2
Article 21240×831 73 KB

Education attainment was also a good predictor of all disorders (including affective psychosis), as shown in the next image.

Article 3
Article 31175×874 77.4 KB

This leads to the logical question of whether the IQ-mental health relationship is just a function of education. The authors found it was not (though controlling for education did weaken the relationship between IQ and mental health). The authors also tested whether the background variables of the parents’ income level and education level could explain the relationship. Again, those other variables could not, though the relationship was weakened. An even stronger control was to only compare brothers within the same family (who share a lot more in common than just parents’ income and education). Still, IQ predicted mental health for most disorders, though not for PTSD and personality disorders.

Article 4
Article 4513×862 49.2 KB

The practical and theoretical implications of this study are important. From a practical perspective, it’s amazing that a short test can predict who is at risk for mental health problems years later. That information can be used to target mental health treatments and prevention measures. Theoretically, this study shows how important IQ is: the test was not designed to predict mental health problems–and yet it does anyway. That shows that intelligence tests are not just measuring a person’s test-taking ability or problem-solving skills. IQ is measuring something really important (assuming you think mental health is important).

Reposted from X: https://x.com/RiotIQ/status/1940798339739427230?s=20

Link to full article (no paywall): https://journals.sagepub.com/doi/10.1177/09567976251347221

2

The pattern is really clear: lower IQ means higher risk for almost every mental disorder. What’s huge is that this still holds true even when comparing brothers in the same family, which rules out things like family income or home environment. This suggests IQ itself (or whatever brain factors underlie it) genuinely protects against mental health problems. The practical takeaway? IQ tests at age 17-18 could help identify people who need extra mental health support before problems develop.

3

The bipolar/mania exception is really interesting since it’s the only disorder where higher IQ doesn’t protect you. This matches other research showing bipolar has different causes than other mental illnesses. The education part matters too: even after accounting for IQ, more education still means better mental health. So staying in school helps beyond just being smart, maybe through structure, social connections, or sense of purpose. Bottom line: both intelligence and education independently protect mental health.