Higher intelligence in adolescence linked to lower mental illness risk in adulthood

Higher cognitive abilities and greater educational achievement in adolescence strongly predict a lower risk of developing mental health conditions later in life. A nationwide study of Norwegian men demonstrated that individuals with lower test scores and less schooling experienced notably higher rates of psychological distress in adulthood. The research was published in the journal Psychological Science.

Previous sociological research has established a strong connection between educational attainment and overall mental well-being. People with advanced degrees generally experience fewer mood and anxiety disorders compared to those who leave school early. At the same time, academic success is intimately tied to a person’s general cognitive abilities, which encompass skills like problem solving, numerical reasoning, and language comprehension.

This overlap leaves an unresolved question regarding the root cause of these health disparities. Researchers wanted to know whether the elevated risk of mental illness associated with leaving school early is actually driven by underlying cognitive traits. To answer this, investigators needed to examine both cognitive test scores and educational attainment simultaneously in a large representative sample.

Historically, most psychological surveys have relied on limited subsets of the population. People grappling with severe psychiatric issues or possessing lower cognitive scores frequently drop out of long-term observational studies. This healthy-volunteer bias creates a skewed understanding of health dynamics within the general public.

To overcome these selection problems, a team of researchers utilized comprehensive national administrative databases. Lead author Magnus Nordmo, a researcher at the University of South-Eastern Norway, collaborated with investigators from the Norwegian Institute of Public Health, Duke University, and the University of Oslo. They aimed to untangle the distinct impacts of teenage schooling and test performance on adult well-being.

The research team examined records from more than 270,000 Norwegian men born between 1970 and 1979. During that era, military service was mandatory in Norway, requiring young men to complete a standardized assessment of their mental abilities around the age of eighteen. The evaluations measured fluid intelligence alongside accumulated knowledge, utilizing tasks that involved word comprehension, pattern recognition, and mathematical reasoning.

After standardizing the military test scores, the researchers tracked these individuals into middle age using national health registries. They reviewed primary care records from when the men were between thirty-six and forty years old to identify formal diagnoses of mental health conditions. These diagnoses included depressive disorders, anxiety, post-traumatic stress disorder, sleep disturbances, substance abuse, and schizophrenia.

The team also accessed educational registry data to determine the highest level of schooling each participant had completed by age thirty-five. Educational categories ranged from compulsory primary schooling to advanced master-level and doctoral degrees. By merging these extensive datasets, the investigators mapped out how adolescent assessments and adult educational levels corresponded with later medical visits for psychological care.

The results demonstrated a steady, upward trend in mental well-being as adolescent cognitive scores increased. Men who scored in the lowest category on the military assessments were roughly three times more likely to receive a mental health diagnosis compared to those in the highest-scoring bracket. Almost thirty percent of the lowest-scoring group experienced a diagnosable condition in adulthood.

Only ten percent of the highest-scoring participants sought primary care for mental health issues. When educational achievement was factored into the analysis, a distinct vulnerability pattern emerged. Earning a university degree offered a protective effect regardless of early baseline test scores.

Men who recorded low cognitive scores and completed only compulsory education experienced the absolute highest rates of psychiatric conditions. Nearly forty percent of this specific demographic group received a diagnosis in middle age. The gap between this highly vulnerable group and the most protected group was vast, reaching almost thirty percentage points.

The researchers also evaluated a popular concept known as hyperbrain theory, which suggests that extraordinarily high intelligence might predispose individuals to psychological turmoil. Earlier surveys of high-IQ society members hinted that extreme cognitive capability comes with a sensitive nervous system that raises the risk of anxiety or depression. The Norwegian population data did not support this hypothesis.

Instead of showing increased vulnerability, men with the absolute highest test scores exhibited the lowest rates of clinical diagnoses for almost every condition studied. The protective effect of high test scores held strong even at the extreme upper end of the score distribution.

There was one notable exception to this general pattern across the diagnostic categories. The rates of affective psychosis, a medical category that includes bipolar disorder, did not align tightly with cognitive test performance. The relationship between adolescent test scores and this specific psychiatric condition was much less pronounced than the dramatic gradients seen for depression or substance abuse.

The investigators wanted to ensure their findings were not merely a byproduct of poverty or challenging home environments, which can depress test scores and harm health. To isolate these variables, the team performed a comparative analysis using data from more than 80,000 brothers. Brothers typically share parents, an adolescent household, and general demographic backgrounds.

When looking exclusively at differences between brothers raised under the same roof, the connection between lower cognitive scores and elevated psychiatric risk persisted. However, the association for certain conditions like post-traumatic stress disorder and personality disorders were not statistically significant in the sibling model. For most other conditions, the within-family analysis suggested that mental health disparities genuinely relate to specific individual cognitive trajectories, not just parental income.

The investigators proposed several possible reasons for this persistent lifelong link. People with lower cognitive test scores frequently end up with lower-paying jobs and fewer educational credentials. This occupational path can lead to difficult working conditions, financial instability, and residence in under-resourced neighborhoods.

These environmental stressors can accumulate over decades, heavily taxing an individual’s psychological resilience. Navigating a modern society that heavily rewards academic and professional achievement might also cause persistent friction for those who struggle in traditional learning environments. Continual underachievement can generate chronic stress, which frequently precipitates severe depressive and anxiety states.

The authors noted that men possessing lower cognitive scores who also leave school early might represent an under-recognized demographic requiring preventative psychological care. Developing specialized support systems for adolescents struggling in academic settings could help mitigate their elevated risk for future psychiatric emergencies. Better occupational counseling and targeted therapy adaptations could improve outcomes for this group.

While the study utilized massive national registries, the research team acknowledged several limitations in their approach. The analysis relied exclusively on primary care diagnoses recorded by general practitioners. This means that men who experienced deep psychological distress but never sought formal medical treatment were completely excluded from the illness counts.

If individuals with higher cognitive abilities happen to handle emotional stress without visiting a doctor, that behavioral avoidance could influence the final health statistics. Additionally, the investigation only included Norwegian men born in a specific decade. Because Norway features a robust universal healthcare system and strong social safety nets, the observed patterns might not translate directly to nations with different economic realities.

Finally, the researchers cautioned against assuming a strictly one-way causal street between adolescent test scores and later mental wellness. Although the psychiatric evaluations occurred nearly two decades after the cognitive tests, some participants may have experienced undocumented psychological distress during early childhood. Early mental distress could disrupt fundamental academic learning, subsequently causing the lower test scores in late adolescence.

The study, “Cognitive Abilities and Educational Attainment as Antecedents of Mental Disorders: A Total Population Study of Males,” was authored by Magnus Nordmo, Hans Fredrik Sunde, Thomas H. Kleppestø, Morten Nordmo, Avshalom Caspi, Terrie E. Moffitt, and Fartein Ask Torvik.