Trace lithium concentrations in mental disorders and suicidal behavior: A cross-sectional study

Studies have demonstrated a negative correlation between lithium trace concentrations in drinking water and suicide rates; however, a study focused on clinical significance of lithium concentrations in individual patients was needed. Therefore, we aimed to assess lithium trace concentrations in individuals with mental disorders and compare them to healthy controls to evaluate whether lithium concentrations are associated with mental disorders and/or suicidal behavior.

We enrolled 50 patients diagnosed with mental disorders without a history of suicidal behavior, 51 patients hospitalized after a suicidal attempt, and 46 healthy individuals as a control group for the analysis and comparison of lithium trace concentrations in blood serum. The suicidality risk was evaluated using the Mini International Neuropsychiatric Interview. Quantile regression (QR) was used to evaluate lithium concentrations (as the outcome) between the control and patient groups (as predictors), along with a set of covariates.

The median of serum lithium concentration overall was 1.76 µg/L (IQR 1.17-3.42); range 0.2-26.95 µg/L. Mutivariable QR analysis, adjusted for age, gender, and suicidality risk, revealed that at the 75th quantile, in patients' lithium concentrations were significantly lower compared to the controls. A high suicidality risk was associated with decreased lithium concentrations at the 75th quantile (B = - 2.073, p = 0.014).

The serum lithium concentrations in the highest quantiles were significantly lower in patients with mental disorders compared to healthy individuals and lower lithium concentrations in serum were associated with a higher risk of suicidality.