To our knowledge, our study is the first to examine the associations between anthropometric indicators for obesity and suicidal ideation among women in a large, population-based, nationally representative sample. Although our study demonstrated a significantly increasing trend in the prevalence of suicidal ideation with increasing levels of the three indicators for obesity, the associations between obesity and suicidal ideation seem to be confounded by having chronic conditions or current depression, either individually (for the association between BMI and suicidal ideation) or jointly (for the associations between waist circumference and WHR and suicidal ideation).
Suicide is one of the leading mental health problems in the world with enormous consequence [42
]. From 1990–1992 to 2001–2003, the prevalence of suicidal ideation, plans, or attempts did not vary much in the US population despite a dramatic increase in treatment [44
]. In 2007, suicide accounted for more than 34,000 deaths and was the 11th leading cause of death in the United States [42
]. Regarding suicidal ideation, results of previous studies showed that the lifetime prevalence of suicidal ideation was 15.6% in the adult US population [40
]. A recent study showed that about 3.7% of US adults (3.5% of men and 3.9% of women) reported having suicidal thoughts in the past year [45
]. Our study further revealed that about 3.0% of US women reported having suicidal ideation in the past 2 weeks.
Multiple risk factors for suicidal ideation or suicidal behaviors have been reported including sociodemographic factors (such as younger age, being female, less educated, and not being married), DSM-IV disorders (such as anxiety disorders, mood disorders, impulse-control disorders, depression, and substance abuse), chronic physical conditions (such as disability, chronic physical pain, terminal illness, and life-threatening diseases), some medications, and firearm ownership [24
]. Previous studies exploring the relationships between BMI and risk of suicide mortality or suicidal behaviors among women have yielded mixed results [6
]. This may have resulted from different study settings with different outcomes assessed (the risk of suicide death versus lifetime or past-year suicidal ideation or suicidal attempts) and different covariates adjusted for. The present study provides further evidence that a high BMI level was associated with an increased likelihood for suicidal ideation among US adult women independent of sociodemographic variables and lifestyle risk factors; however, this positive association no longer existed after taking into consideration the chronic conditions or current depression status as demonstrated in the present study. Importantly, our results also showed that both chronic conditions and current depression were significantly associated with suicidal ideation. Thus, the previously reported association between BMI and suicidal ideation may have been confounded by existence of obesity-related chronic conditions or depression, which deserves further investigation.
The strength of the present study is that we were able to simultaneously assess the relationships between abdominal obesity as measured by waist circumference and WHR and suicidal ideation. Abdominal obesity has been shown to be associated with impaired health, impaired quality of life, and psychiatric disorders [5
]. However, results of a previous study showed that waist-hip ratio was not a predictor of suicide mortality among 46,755 male participants in the Health Professionals Follow-up Study [12
]. Results of the present study demonstrated that both waist circumference and waist-height ratio were positively associated with suicidal ideation among US adult women irrespective of having either chronic conditions or current depression; however, as shown for BMI, these associations appeared to be confounded jointly by chronic conditions and current deperssion.
Studies have shown that both physical conditions and mental disorders are associated with higher risks for suicidal ideation or suicidal behaviors [40
]. Our findings that the associations between obesity indicators (i.e., BMI, waist circumference, and waist-height ratio) and suicidal ideation diminished in the present study after controlling for either chronic conditions or current depression or both suggest that impaired physical health or mental disorders may have individually (for overall obese women) or jointly (for abdominally obese women) contributed to an increased risk for suicidal ideation among obese population.
Our study has several limitations. First, suicidal ideation was assessed based on self-report of a single item on the PHQ-9 and thus subject to recall bias. Second, although we have included a number of physical chronic conditions in our analyses, the severity of each individual chronic condition was unknown, so we were unable to weigh differently the impact of a specific chronic condition on the association between obesity indictors and suicidal ideation. Third, we assessed the potential role of current depression in confounding the relationship of obesity with suicidal ideation in the present study; however, we were unable to evaluate the possible effects of other psychiatric disorders, antipsychotic medication use, emotional functioning, social support, and family history of suicidal behaviors on the association due to lack of data. Finally, potentially protective factors including life satisfaction, social support, and coping were not assessed either.
In conclusion, our results from this large, population-based study suggest that depression and chronic physical conditions may explain much of the association between obesity and suicidal ideation among US adult women. Although the exact mechanisms mediating the association between obesity and suicidal ideation remain to be elucidated, results from the present study may have important implications for preventing suicidal ideation. Our findings suggest that combined intervention programs targeting obesity management and the prevention/treatment of obesity-related physical chronic conditions and depression may help to reduce the prevalence of suicidal ideation and ultimately reduce risk of suicide mortality. Currently, obesity among US adults is a major public health concern after decade of increase in its prevalence [2
]. Thus, efforts on screening and assessing obesity-related physical and mental disorders may provide useful information for preventing suicidal behaviors in this population.