Large-scale Study Examines Link Between IQ Level and Attempted Suicide

Men with a low IQ in early adulthood are at a higher risk for attempted suicide later in life, researchers from the Karolinska Institute, led by Dr. Finn Rasmussen, have found.

In a large-scale study of more than 1.1 million men, Rasmussen and colleagues found that nearly 18,000 of these men (1.6%) were admitted to the hospital at least once for an attempted suicide during 24 years of follow-up, which began after their IQ had been tested. Men with the lowest IQ scores from early adulthood were about nine times as likely to attempt suicide as men with the highest IQ, and “there was a stepwise increase in risk across the full IQ range,” according to the researchers. They also note that “similar associations were observed for all specific methods of attempted suicide.”

A separate analysis revealed that there was no link between IQ level and attempted suicide risk in men who had been diagnosed with psychosis before they tried to take their own lives.

Though the researchers did not find a specific reason for the link between IQ level and attempted suicide risk, they did speculate about some possibilities. One suggestion was that because people with a lower IQ tend to have a lower socioeconomic status and income level, they may face more financial and social hardships, leading to more suicidal behaviors and thoughts. Additionally, unhealthy lifestyle choices, such as binge drinking, have been linked to lower IQ, and this habit could impact the frequency of suicidal thoughts; other studies have suggested that exposure to violence in childhood hampers IQ development and can also influence later risk for suicide. The researchers note in the British Medical Journalthat “a greater understanding of the mechanisms underlying these associations may provide opportunities and strategies for prevention.”