Lithium in drinking water and suicide prevention: The largest nationwide epidemiological study from Japan.

OBJECTIVES: The aims of the present study thus were (a) to further investigate the association between lithium levels in drinking water and suicide rates by adjusting relevant factors using the so far largest available dataset in Japan, (b) to confirm sex differences, (c) to estimate the effects of long-term exposure to trace lithium, (d) to investigate the effects of drinking bottled instead of tap water, and (e) to exploratorily investigate which lithium levels may be associated with lower suicide rates. METHODS: Mean lithium levels in drinking water of all 808 cities and wards (ie, 785 cities of 46 prefectures and 23 wards of Tokyo) in Japan were examined in relation to mean suicide standardized mortality ratios (SMRs) during the 7 years from 2010 to 2016. Multiple regression analyses adjusted for the size of each population were used to investigate the association of lithium levels with suicide SMRs with adjustments for relevant factors. RESULTS: The adjusted model showed significant inverse associations of lithium levels with total and male SMRs, but not with female SMRs. Neither the proportion of residents who continued to live in the same city nor the consumption of bottled water changed the association between lithium levels and suicide SMRs. Finally, it was 30 µg/L or more that was associated with lower suicide SMRs. CONCLUSIONS: The present findings reconfirm the inverse association between lithium levels in drinking water and suicide rates particularly in the male population.

Increased volume of the left hippocampal dentate gyrus after 4 weeks of bright light exposure in patients with mood disorders: a randomized controlled study.

Bright light exposure (BL) induces neurogenesis in the rat hippocampal dentate gyrus (DG). We had previously conducted a randomized controlled trial (RCT) in which a 4-week period of BL in healthy participants resulted in increased volume of the left DG-head. This study aimed to investigate the effects of BL on the DG in patients with mood disorders. A 4-week RCT was conducted in which patients with mood disorders were randomly assigned to either a BL group (10,000 lx) or dim light exposure group (DL group; 50 lx). All patients underwent clinical assessment and magnetic resonance imaging at baseline and after the intervention. The study registration number is UMIN000019220. Our final sample included 24 patients (BL group, n = 12; DL group, n = 12). A significant effect of time and group was detected in the volumes of the left DG-head (F (1, 22) = 11.6, partial η2 = 0.35, p = 0.003) and left DG-total (left DG-total = left DG-head + left DG-body; [F (1, 22) = 6.5, partial η2 = 0.23, p = 0.02]). Additionally, the BL group demonstrated a significant increase in the volume of the left DG-head (95% CI: -5.4 to -1.6, d = 1.2, p = 0.002) and left DG-total (95% CI: -6.3 to -1.5, d = 1.06, p = 0.005) as well as a positive correlation between the percentage change in the volume of the left DG-total and the percentage change in the scores of the mood visual analog scale (r = 0.58, p = 0.04). In conclusion, our study results suggest that compared to DL, BL leads to a significantly greater increase in the left DG volume in patients with mood disorders. This increase in the left DG volume may be associated with mood improvement in the patients.

Increase in the left hippocampal dentate gyrus head volume after a 4-week bright light exposure in healthy participants: A randomized controlled study.

INTRODUCTION: Bright light therapy (BLT) has been used for treating seasonal affective disorder, depression and bipolar depression. However, it's precise mechanism remains unclear. Bright light exposure (BL) induces neurogenesis in the adult rat hippocampal dentate gyrus (DG). We hypothesized that BL may induce neurogenesis in the human DG as well. METHOD: A 4-week randomized controlled trial study was conducted, where healthy participants were randomly assigned to a BL group (10,000 lux) or dim light exposure group (DL group; 50 lux). Magnetic resonance imaging was performed at baseline and after 4 weeks. Longitudinal hippocampal subfield segmentation was generated via the FreeSurfer 7.1.1 hippocampal subfields module to evaluate volume of bilateral granule cell and molecular layer of the DG-head and -body. RESULTS: Our final sample size was 20, which consisted of BL group (n = 10) and DL group (n = 10). After age and sex adjustment, significant effects of time and group were detected in the left DG-head volume (p = 0.04). In the BL group, the left DG-head volume significantly increased (p = 0.004), whereas no significant volumetric change was observed in the DL group. CONCLUSIONS: This study revealed that 4-week BL significantly increased left DG-head volume in healthy participants. Thus, neurogenesis might be induced by BL in the human DG, which is a completely new mechanism of BLT.