Despite being a wealthy country, clean water crises continue to plague the US. Late last week, residents of Jackson, Mississippi filed a class action lawsuit over a major water crisis that left 150,000 people in the capital city without clean running water. The crisis started after major flooding in August, but follows years of neglect to the infrastructure in the majority-Black city. Simultaneously, an arsenic scare in New York City’s Jacob Riis Houses further sounded the alarm on critical updates to aging water infrastructure.

Arguably the biggest water wake-up-calls have come from the city of Flint, Michigan. On April 25th, 2014, the city government switched its water supply from Lake Huron and the Detroit River to the Flint River. The water supply then wasn’t properly treated to prevent lead and other elements from leaching out of the city’s old water pipes and into the drinking water. Virtually all Flint residents were consequently exposed to drinking water with unsafe levels of bacteria, disinfection byproducts, and lead (a neurotoxicant).

Now, a new study published in the journal JAMA Network Open reveals the serious mental toll that these water crisis can have on the residents affected. The study looked at data from the largest mental health survey of the Flint community. In the five years after the water crisis began, one in five adults (about 13,600 people) were estimated to have clinical depression, and one in four (about 15,000 people) were estimated to have post-traumatic stress disorder (PTSD) five years after the water crisis began.

[Related: Michigan health director charged with involuntary manslaughter due to Flint water woes.]

“The mental health burden of America’s largest public-works environmental disaster clearly continues for many adults in Flint,” said Aaron Reuben, a postdoctoral scholar at Duke University who led the research, in a press release.

The drinking water in Flint wasn’t declared lead-free until January 24, 2017, but residents were cautioned that it could take over a year for the water to be completely safe. Tens of thousands of children and adults developed high blood-lead levels, putting them at greater risk for cognitive deficits, mental health problems, and other health problems later in life.

“We know that large-scale natural or human-caused disasters can trigger or exacerbate depression and PTSD,” said Dean Kilpatrick, a psychiatry professor at the Medical University of South Carolina and senior author of the study, in a press release. Kilpatrick noted that there was evidence of high rates of mental health problems in the community during the first years of the crisis. “What we did not know until now was the extent to which Flint residents continued to have mental health problems at the clinical diagnosis level five years after the crisis began.”

Past year rates of depression and PTSD identified in Flint and today they are three to five times greater than national estimates among US adults overall, according to Kilpatrick. This is likely due to a combination of higher base rates of mental health problems in Flint (lower incomes and systemic poverty, for example) before the crisis and significant exacerbation of problems resulting from the crisis.

[Related: The devastating effects of childhood lead exposure could last a lifetime.]

“The vast majority of our respondents were never offered mental health services despite clear indication that the crisis was psychologically traumatic. Now that pipes are being replaced, the time is right to begin a second phase of recovery from the water crisis – one that focuses on providing additional resources to heal psychological wounds,” Reuben added.

The findings in this study suggest that more should be done to provide mental health treatment for residents of Flint. “There is a clear unmet need. Nearly 100 percent of surveyed Flint residents reported that they changed their behavior to avoid consuming contaminated water during the crisis, and the vast majority still worry that the exposures they had may cause future health problems for themselves or their family members,” concluded Reuben.

While this problem isn’t unique to Flint, the city and its people shone a glaring spotlight on a nationwide issue. One of the enduring faces of this Flint crisis is Mari Copeny aka Little Miss Flint. At eight years-old, she wrote a letter to then President Barack Obama to draw attention to the crisis. The president shared that “letters from kids like you are what make me so optimistic about the future” and he visited Flint in 2016. Now 15 years-old, Copeny has continued to advocate for environmental justice and even launched a GoFundMe to raise money for Jackson residents.