The impact of drinking water quality on mental health and the modifying role of diet

In a recent study published in BMC Medicine, researchers estimate how exposure to various trace elements in drinking water increases the risk of depression and anxiety.

Study: Association between drinking water quality and mental health and the modifying role of diet: a prospective cohort study. Image Credit: New Africa / Shutterstock.com

Background

Mental health disorders, particularly depression and anxiety, remain a leading cause of both disability and premature death throughout the world. Following the coronavirus disease 2019 (COVID-19) pandemic, the prevalence of both anxiety and depression throughout the world rose by about 25%, thus exemplifying the widespread prevalence of these mental diseases.

Several factors may increase an individual’s risk of depression or anxiety, including genetics, social environment, and physical environment. Within the physical environment, exposure to heavy metals like cadmium has been shown to increase the risk of depression and anxiety, whereas other elements like manganese, copper, and selenium, all of which combat oxidative stress, have the potential to reduce the risk of depression.

To date, most studies investigating the impact of environmental risk factors on the incidence of depression and anxiety have been cross-sectional. Within China, few longitudinal studies have examined how exposure to metal and nonmetal elements in drinking water may impact the risk of depression and anxiety.

About the study

In the present study, researchers identified people diagnosed with depression and anxiety from the Yinzhou district using International Classification of Disease codes F32 and F41, respectively, in data retrieved from the Yinzhou Health Information System (YHIS). Atomic absorption spectrophotometry (AAS) was used to measure manganese, zinc, copper, iron, aluminum, cadmium, selenium, and fluorine levels in tap water samples collected from 37 sites in the Yinzhou district. 

Water samples were collected four times each year, with at least one sample collected each season. Exposures were assigned to participants based on their residential addresses and the location of tap water collection sites. Daily exposure to all trace elements in drinking water was calculated and adjusted based on the daily drinking water intake of participants, as well as their age and gender.

A baseline survey was administered to collect data on participants’ frequency of consuming leafy vegetables, meat, fruits, and fish, with their intake of these dietary components categorized as low, moderate, or high. Data on sociodemographic status, lifestyle, and medical history were also acquired.

Study findings

The final analysis included 24,285 individuals between 2016 and 2021 without a history of depression or anxiety. From these individuals, 765 and 1,316 depression and anxiety cases, respectively, were reported during a median follow-up period of 4.72 and 4.68 years, respectively.

Females, as well as those who never smoked or drank, were more likely to have depression, in addition to a greater risk of hypertension, dyslipidemia, cancer, and stroke. Comparatively, females, less educated individuals, older individuals, never drinkers, non-smokers, and those with a lower income were more likely to have anxiety, diabetes, dyslipidemia, cancer, and stroke, in addition to lower levels of seafood and meat consumption.

Exposure to aluminum in drinking water was more commonly reported in individuals diagnosed with depression, whereas exposure to manganese, iron, and aluminum in drinking water was higher in individuals with anxiety. Individuals with anxiety were also exposed to lower levels of zinc as compared to healthy participants.

Long-term exposure to zinc, iron, aluminum, selenium, and fluorine did not impact the risk of depression. Likewise, long-term exposure to zinc, copper, aluminum, cadmium, and fluorine did not increase the risk of anxiety.

Diet did not have a significant effect on the relationship between the risk of depression and manganese, copper, and cadmium exposure in drinking water. However, the risk of anxiety was greater in individuals who consumed less fruits, more seafood, and meat and who were also exposed to manganese and iron in drinking water. Long-term exposure to copper, selenium, and fluorine was also associated with a greater risk of anxiety in individuals who consumed less leafy vegetables and fruits.

Lower socioeconomic level was associated with increased exposure to heavy metals, particularly copper, in drinking water. Additionally, older, low-income, and less educated individuals who were exposed to cadmium in drinking water were also at a greater risk of depression.

Higher education levels were more commonly observed in anxious individuals who were exposed to manganese and selenium in drinking water. Comparatively, exposure to iron in drinking water was also more common in older and less educated individuals with anxiety.

Conclusions

The present study findings underscore the need to improve the quality of drinking water and adopt healthy dietary habits to reduce the burden of depression and anxiety, as these measures may contribute to the pathophysiology of depression and anxiety. Public health policies should also address the inequitable effect of exposure to various trace elements in drinking water in relation to the increased risk of mental diseases among people in low socioeconomic strata.