Probing the Link Between Mood Disorders and Lithium in Water Supplies

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Researchers have explored the relationship between exposure to lithium in drinking water and rates of bipolar disorder in the community.
Researchers have explored the relationship between exposure to lithium in drinking water and rates of bipolar disorder in the community.

While lithium is a mainstay of treatment in bipolar disorder, findings from animal studies have shown that subtherapeutic lithium levels may also affect mood. In the same vein, multiple studies have investigated the possibility that lithium in drinking water may influence mood and other outcomes relevant to psychiatric and public health. 

Research from multiple countries, including the United States, has demonstrated a link between higher lithium levels in drinking water and lower rates of suicide in clinical and general populations. Findings from other countries, however, indicate no such association.

A recent nationwide population-based study explored whether long-term exposure to low levels of lithium via drinking water may serve as primary prophylaxis in the development of bipolar disorder in the general population in Denmark.1 Researchers from several Danish universities expected to find an inverse association between higher levels of long-term exposure and lower rates of bipolar disorder.

The sample consisted of patients with previous hospital contact from 1995 to 2013 with a mania/bipolar disorder diagnosis (n=14,820), as well as 10 controls matched for age and gender from the general population (n=140,311).

The investigators examined longitudinal data on each individual's municipality of residence, lithium levels in the drinking water, and certain time-specific data, and estimates of average lithium exposure from drinking water were calculated for all participants. The average lithium exposure in the clinical group was compared with that in the general population.

Contrary to the hypothesis, the results revealed no difference in the average median amount of lithium exposure between clinical participants and controls (12.5 μg/L; interquartile range [IQR]: 7.6-15.7 μg/L; P =.2). In addition, there was no reduction in the incidence rate ratio of mania/bipolar disorder with higher long-term exposure or by age bracket (age 0-40, 41-60, and 61-100).

Although no association was observed between lithium in drinking water and the incidence of bipolar disorder in this particular study, the investigators concluded that the topic warrants investigation in areas that have higher lithium levels in drinking water compared with Denmark.

To further explore the concept of lithium in drinking water as a potential psychiatric prophylactic, Psychiatry Advisor consulted Michael E. Thase, MD, professor of psychiatry and director of the Mood and Anxiety Program at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.

Psychiatry Advisor: Overall, what does the research suggest about the relationship between lithium in drinking water and measures of mental illness?

Dr Thase: There is older literature, including a study done in Texas and another conducted in one region of Japan, that does suggest that suicide rates are lower in regions in which there is a higher concentration of lithium in the drinking water. 

[Editor's note: The Texas study, published in 2013 in the Journal of Psychiatric Research, adjusted for potential socioeconomic confounders, noting that previous studies on the topic had been criticized for failing to do so.2 The results demonstrated lower suicide rates in counties with higher lithium levels in the public water supply. In research conducted in Japan and reported in 2015 in the Journal of Clinical Psychiatry, there was an inverse association (β = .169, P = .019) between lithium in drinking water and standardized mortality ratios (SMRs) of male suicide but not female or total SMRs.3 A 2013 study from a different region of Japan found similar results for females only.4]

It is an intriguing association, but not all articles are positive and the amount of exposure to lithium via drinking water is much, much lower than the exposure from lithium therapy.

The recent paper by Kessing and colleagues in Bipolar Disorders suggested there was no beneficial effect in bipolar disorder. Specifically, the paper found no association between the amount of lithium in drinking water in different regions of Denmark and the risk of developing bipolar disorder. A related paper by the same group published in a different journal likewise found no association between drinking water containing lithium and the risk for suicide in Denmark.5  

The Danish findings support a skeptical approach, although as noted in a related commentary the average levels of lithium in the water in Denmark are much lower than in the areas of Texas and Japan that seemed to show an effect in the earlier studies.

Psychiatry Advisor: Are there any other potential benefits or issues with adding lithium to drinking water?

Dr Thase: There is some evidence that higher lithium levels may protect against dementia.

[Editor's note: In another study by the same group in Denmark, with a sample of 73,731 patients with dementia and 733,653 controls with a median age 80.3, a significant difference in lithium exposure was noted in patients (median, 11.5 µg/L;IQR: 6.5, 14.9 µg/L) compared with controls (median, 12.2 µg/L; IQR: 7.3, 16.0 µg/L; P <.001).6]

Whereas suicide is a relative low risk in the general population (fewer than 1% will die from suicide), the ultimate reward for longevity is a progressively increasing risk for dementia, exceeding 25% by age 90.

That said, any effort to improve public health by adding lithium to our drinking water will require great care to ensure that we are not trading risks as thyroid disease, acne, psoriasis, one type of congenital heart disease, and kidney disease are all associated with chronic lithium exposure.

References

  1. Kessing LV, Gerds TA, Knudsen NN, et al. Lithium in drinking water and the incidence of bipolar disorder: a nation-wide population-based study. Bipolar Disord. 2017;19(7):563-567.
  2. Blüml V, Regier MD, Hlavin G, et al. Lithium in the public water supply and suicide mortality in Texas. J Psychiatr Res. 2013;47(3):407-411.
  3. Ishii N, Terao T, Araki Y, et al. Low risk of male suicide and lithium in drinking water. J Clin Psychiatry. 2015;76(3):319-326.
  4. Sugawara N, Yasui-Furukori N, Ishii N, Iwata N, Terao T. Lithium in tap water and suicide mortality in Japan. Int J Environ Res Public Health. 2013;10(11):6044-6048.
  5. Knudsen NN, Schullehner J, Hansen B, et al. Lithium in drinking water and incidence of suicide: a nationwide individual-level cohort study with 22 years of follow-up. Int J Environ Res Public Health. 2017;14(6):627.
  6. Kessing LV, Gerds TA, Knudsen NN, et al. Association of lithium in drinking water with the incidence of dementia. JAMA Psychiatry. 2017;74(10):1005-1010.
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