A surprising study has found that nuclear disasters wreak havoc on individuals — not physically, however, but rather mentally.

People who have had to deal with a modern nuclear accident have rarely had to suffer physically with radiation effects — instead, mental illness is a bigger risk, according to new research as reported by Medical News Today.

Dr. Koichi Tanigawa, who works at the Fukushima Medical University in Japan, said that a good example lies in the recent Fukushima meltdown incident a few years ago. The radiation dose to the public ended up being very low, with very little physical health effects expected. But the psychological and social effects of the disaster had a “devastating impact” on the lives of those individuals, according to the report.

A total of 437 nuclear power plants are situated around the world, but nuclear accidents are extremely rare, with Fukushima Daiichi’s meltdown after a severe earthquake in Japan back in 2011 being the most recent example. Only four other severe nuclear accidents have been rated at least a level 5 in terms of devastation: the infamous Chernobyl meltdown in Russia in 1986, the Three Mile Island incident in the United States in 1979, as well as Windscale Piles in the UK and Kyshtym in Russia, both in 1957.

That’s a pretty low failure rate — the only problem is, when it comes to nuclear, any failure is potentially devastating. And even though even those incidents didn’t result in widespread health problems, with the exception of Chernobyl, the mental stress of such events can be incredible on the general population.

Poor communication about what health risks are involved only make the problem worse, as people don’t know what to expect and have no idea what radiation levels might be or what effect they might have.

The study found that even 20 years after an accident, rates of depression and post-traumatic stress disorder remained shockingly high.