Association between chronic ambient heavy metal exposure and mental health in Korean adult patients with asthma and the general population.

Background: Insufficient evidence is available to confirm the effect of exposure to airborne metals on mental disorders, particularly among asthmatics. We aimed to investigate the effect of airborne metal exposure on mental health responses in asthmatics and the general population.

Methods: Using nationally representative cross-sectional data, a total of 47,796 adults were analyzed. We assessed the associations between mental health factors, such as perceived stress, depressive symptoms, and suicidal ideation, and individuals' annual average exposure to airborne metals, including lead, cadmium, chromium, copper, manganese, and iron, over 14 years using multiple logistic regression. The associations were compared using the propensity score matching (PSM) method. The odds ratios (OR) and 95% confidence intervals (CI) for mental health outcomes were calculated for an interquartile range (IQR) increase in the concentration of each airborne metal.

Results: Exposure to airborne metals was significantly associated with increased odds of adverse mental health in asthmatics. Significant associations between all ambient heavy metal contaminants and suicidal ideation were found in both asthmatic patients and the general population. After PSM, exposure to all ambient heavy metal contaminants showed significant associations with suicidal ideation in patients with asthma, whereas only iron exposure was significantly associated with suicidal ideation in the general population. After adjusting for perceived stress and depressive symptoms, similar patterns were also observed. Exposure to lead (OR: 1.99; 95% CI: 1.45-2.72) showed particularly a strong association with suicidal ideation in asthmatics.

Conclusions: This study suggests that exposure to airborne metals significantly increases depressive symptoms and suicidal ideation, especially in individuals with asthma. Additional clinical research is needed to better understand these associations.