Lithium occurs naturally in food and water. While low environmental concentrations in drinking water are associated with mental illnesses and behavioral offences, at therapeutic dosages it is used to treat psychiatric disorders, partly by facilitating serotonergic (5-HT) neurotransmission. However, as little is known about the physiological role of nutritional lithium for neurobiological functioning and emotional processing in the general population, endogenous lithium concentrations were hypothesized to be associated with measurable effects on emotional liability and the loudness dependence (LD) that is proposed one of the most valid indicators of 5-HT neurotransmission.

Auditory evoked potentials (AEP) of healthy volunteers with either high or low lithium serum concentrations were recorded using multi-channel EEG. Emotional liability was assessed using the Brief Symptom Inventory (BSI).

Serum lithium concentrations varied widely, low levels correlating with symptoms of Somatization. While there were no significant correlations between LD and lithium concentrations, LD correlated positively with Paranoid Ideation, and in the high-lithium group inversely with further aspects of emotional liability (Depression, Psychological Distress).

Effects of low levels of endogenous lithium are associated with an increase in emotional liability, and high levels with some protective effects. Findings on the mediating neural correlates point to the 5-HT system, but remain inconclusive regarding LD. Potential benefits of endogenous lithium as a neurobiological trace element on neurobehavioral functioning especially in high-risk individuals would have public health implications.