Updated

Experts say that mental distress could be one of the biggest health problems to emerge from the nuclear disaster in Japan two years ago.

A tsunami swamped the Fukushima Dai-ichi nuclear plant on March 11, 2011, knocking out cooling systems and causing meltdowns and explosions.

The cancer risks from the radiation remain unclear, but the crisis is already exacting a psychological toll. A quarter of 35,300 respondents to a Fukushima Medical University questionnaire indicated they were experiencing high levels of stress or trauma.

Many families are split: The fathers are living at home for their jobs, while mothers and children have moved to temporary shelters or government-sponsored housing away from the radiation.

Mental distress was a significant health issue after Three Mile Island in 1979 and Chernobyl in 1986.