Intelligent people (≥130 IQ) have a lower risk of mental illness than average people (85-115 IQ), while unintelligent people (≤70 IQ) have a significantly higher risk.

"Studies reporting that highly intelligent individuals have more mental health disorders often have sampling bias, no or inadequate control groups, or insufficient sample size. We addressed these caveats by examining the difference in the prevalence of mental health disorders between individuals with high and average general intelligence (g-factor) in the UK Biobank."

Source: High intelligence is not associated with a greater propensity for mental health disorders (2022, n = >250,000)