Underweight individuals are at an increased risk of suicide, study finds

An analysis of the Korean National Health Insurance Service database found that underweight individuals are 44% more likely to die by suicide compared to their normal-weight peers. In contrast, overweight and obese individuals were 20–30% less likely to die by suicide than those of normal weight. The research was published in BMC Psychiatry.

Suicide—the act of intentionally ending one’s own life—is a major public health concern worldwide. It typically results from a complex interplay of mental health conditions, such as depression, anxiety, or substance use disorders, along with social, emotional, or economic stressors.

Although suicide can affect individuals across all age groups, rates tend to be especially high among adolescents, the elderly, and marginalized populations. Suicide not only ends a life, but also leaves a profound impact on families, friends, and communities. Prior research has identified a wide range of genetic, social, and physical factors associated with suicide risk. These include specific genetic variants affecting brain systems that use the neurotransmitter serotonin, as well as social factors such as living alone, introverted personality traits, exposure to trauma, and financial hardship. Chronic medical and psychiatric conditions—such as depression, migraine, sleep apnea, and insomnia—are also linked to an increased risk of suicide.

Study author Joonyub Lee and his colleagues examined the relationship between body weight—measured by body mass index (BMI)—and suicide risk among South Koreans. The researchers emphasized the importance of this investigation, noting that South Korea is currently facing a rapid and unprecedented rise in both suicide rates and obesity prevalence.

The team analyzed data from the National Health Information Database (NHID), a comprehensive database in South Korea that includes health examination results and insurance claims. The study sample included 4,045,081 adults over the age of 19 who underwent a national health screening in 2009. These individuals were followed from 2009 through the end of 2021—or until death by suicide, if it occurred during the study period.

In their analysis, the researchers considered participants’ BMI, waist circumference (as a measure of abdominal obesity), and diagnoses of depression, schizophrenia, anxiety disorders, and eating disorders, along with a range of other medical conditions. They also factored in alcohol consumption, household income, and levels of blood glucose and serotonin.

The results showed that individuals who were underweight had a 44% higher risk of dying by suicide compared to those with normal weight. On the other hand, those who were overweight or obese had a 21% and 29% lower risk, respectively. These associations remained significant regardless of whether participants had been diagnosed with depression or lived alone.

“Suicidal death risk was inversely correlated with BMI [body mass index] categories, independent of MDD [major depressive disorder] or living arrangements. Our data suggests the importance of physiological factors associated with body mass in understanding suicidal death risk,” the study authors concluded.

The study contributes to the scientific knowledge about links between suicide and body mass index. However, it should be noted that the study was conducted in South Korea. Results might not be the same in other countries.

The paper, “Inverse association between obesity and suicidal death risk,” was authored by Joonyub Lee, Seung-Hwan Lee, Mee-Kyoung Kim, Hyuk-Sang Kwon, Jae-Seung Yun, Yeoree Yang, KunHo Yoon, Jae-Hyoung Cho, Chi-Un Pae, Kyungdo Han, and Jang Won Son.