Psychological distress and intelligence in young men

• Symptoms of psychological distress are generally low among 18–19 year-old Danish men.
• The association between distress and IQ is a non-linear negative function.
• Men above the 90th percentile for distress have IQs averaging 94.

This study has primarily aimed to investigate first, the prevalence of psychological distress complaints among a population-representative sample of young men, second, whether psychological distress is associated with poorer performance on an intelligence test and third, whether any association is a purely linear function. Specifically, we have examined self-reported symptoms of psychological distress, and IQ, among 1869 young men appearing before the Danish Draft Board with a view to assessing suitability for conscription. The assessment included a 25-item questionnaire concerning a broad range of distress-related items, the Personal Health Schema (PHS), having yes/no responses, together with a general IQ test, the Børge Prien's Prøve (BPP). The rate of endorsement of the PHS items was low, ranging between 3% and 29% with a median of two/three items. The Pearson correlation between the two variables was 0.15, but the relationship was better described by a model incorporating a negatively accelerating quadratic function and individuals above the 90th percentile on the PHS had a mean IQ of 94. This finding confirms the need to consider any general psychological distress, especially at high levels, when interpreting intelligence test scores.