Association Between Hair Lithium Levels and Suicide: A Case-Control Study

OBJECTIVE: Hair analysis has emerged as a promising strategy for long-term monitoring of trace elements, offering advantages such as stability and ability to reflect chronic exposure including in cases of postmortem studies. Past research has linked low hair Li levels to mental illness and violent behavior, but no research studies have explored its relationship with suicide. METHODS: A case-control study involving deceased individuals was conducted, analyzing hair samples from 25 suicide cases (59 ± 14, 31-88 years) and 27 non-suicide controls (67 ± 13, 42-94 years). Hair samples were collected, over a three-month period during consecutive forensic autopsies, processed following standardized procedures, and Li analyzed by Inductively Coupled Plasma-Mass Spectrometry. RESULTS: Lithium concentration in hair samples ranged from <3 to 42 µg/kg, after excluding two outliers. No significant differences in Li hair content were found between the suicide and control groups (7 ± 10 µg/kg and 10 ± 11 µg/kg, respectively; F1 (1,50 = 0,748, p = 0,391). After adjustment for sex, age, and mental disorder, the presence of a mental disorder remained significantly associated with suicide (OR, 22.74; 95% CI, 2.18 to 237.19; p = 0.009). CONCLUSION: In the groups studied the hair Li concentrations do not differ between suicide group and controls in this specific population, with low variability and exposure range and no association was found between hair Li and suicide.