Published: December 2015, updated July 2017
Correlational studies suggest that trace amounts of lithium in drinking water may have beneficial health effects, and in particular may reduce suicide rates.1 If the effect is real and there are no adverse health consequences, adding trace lithium to drinking water might save thousands of lives per year.2 However, this effect has not been tested by experimental or quasi-experimental studies, and little research has examined whether trace lithium in water is safe in all populations.3
The Open Philanthropy Project is interested in learning:
- What is the feasibility and cost of conducting studies on the impact of trace lithium on suicide rates with significantly stronger identification than studies completed to date? Examples might include, e.g., a regression discontinuity study or a prospective cohort study.
- What is the feasibility and cost of conducting the first cluster-randomized trials on this question? If adding lithium to a water supply is ethically problematic, could a study be done that experiments with removing differing amounts of lithium from a water supply?
- What studies would need to be conducted to establish that trace lithium in drinking water is (or is not) safe for all populations?
If you have conducted or have considered conducting research on this topic, and you feel you can speak to these questions, we’d like to speak with you. We’re particularly interested in discussions with researchers who might be able to eventually conduct a randomized trial, though we recognize that it may be appropriate to pursue other research strategies first.
We are not yet confident enough in the expected value of further research on this topic to formally issue a request for proposals, but we would like to hear from researchers who are looking for funding for data collection or trials in this space.
Please email firstname.lastname@example.org if you’d like to discuss this.
Update from July 2017: We recently learned of a new study (Knudsen et al. 2017) which studies this question with a stronger identification strategy and a larger sample size than past studies have, and it finds no apparent effect of trace lithium on suicide rates. We have not examined this new study closely, but it makes us substantially less optimistic about there being a true effect. Going forward, we still intend to occasionally check whether this new result has held up, and whether other results (with similarly strong or stronger identification) have been published.
- 1. After learning about this topic from a New York Times piece by Anna Fels, we conducted a shallow review of the literature on whether trace lithium in water might reduce rates of suicide. (Other potential health effects of trace lithium have been studied to some extent, but not as much as the effect on suicide rates has been.) We reviewed three recent reviews of the literature on this topic (Mauer et al. 2014; Vita et al. 2015; Lewitzk et al. 2015), read the ecological studies they cited on trace lithium and suicide, and found two additional ecological studies (Ishii et al. 2015; Neves et al. 2014). Our impression from this literature is that the most persuasive studies (Kapusta et al. 2011; Blüml et al. 2013; Ishii et al. 2015, plus follow-up analyses of the same data) generally found that higher levels of trace lithium were associated with lower age-adjusted suicide rates, at least for men (who commit suicide more often than women), and at least under most sets of statistical controls attempted so far. The ecological studies which failed to find an effect may have done so due to smaller sample sizes and very low levels of naturally occurring lithium in the regions they studied (compared to those of the studies which found an association). We also note that a beneficial effect of lithium on suicide rates has some prior plausibility because lithium is already used in clinical doses (500-1,000 times higher than the trace amounts naturally found in drinking water) to treat psychiatric disorders by stabilizing patients’ mood (see our conversation with Nestor Kapusta). We are not aware of any experimental or quasi-experimental studies on the effects of trace lithium on suicide.
- 2. One factor that increases our interest in this potential intervention is that the strategy for delivering the intervention to whole populations seems unusually straightforward, since lithium is abundant (e.g. see here) and could be added to water supplies a la water fluoridation. Our initial back-of-the-envelope calculations suggest that if either of the models in Kapusta et al. (2011) or Blüml et al. (2013) are roughly correct, a small increase in the amount of trace lithium in drinking water in the U.S. could prevent >4,000 suicides per year.
- 3. A conversation with Professor Nestor Kapusta, September 14, 2015.