Aftermath: Miyako, in Iwate prefecture after the tsunami in March 2011.

Aftermath: Miyako, in Iwate prefecture after the tsunami in March 2011. Photo: Reuters

Tokyo: One in four  preschool-aged children caught up in Japan's 2011 tsunami disaster has psychiatric problems, a report says, with experts warning the effects could last a lifetime if left untreated.

Researchers found 25.9 per cent of children aged between 3 and 5 suffer from symptoms including vertigo, nausea and headaches, with some exhibiting worrying behaviour such as violence or withdrawal.

The Health Ministry study said youngsters were scarred by losing friends, seeing their homes collapse, by separation from parents or by the sight of the huge wall of water that crashed ashore, Japanese newspaper Mainichi Shimbun reported.

Paying respect at Fukushima, one year on: More than 18,000 people died when the tsunami hit.

Paying respect at Fukushima, one year on: More than 18,000 people died when the tsunami hit. Photo: Reuters

The team, led by professor Shigeo Kure of Tohoku University School of Medicine, said young children who do not receive necessary care could develop much worse problems in later life. These could include developmental disorders and learning disabilities, which would have a knock-on effect on academic achievement and employment prospects, it said.

More than 18,000 people died when a 9.0-magnitude sub-sea earthquake sent a towering tsunami into Japan's north-east coast in March 2011.

The country's worst post-World War II disaster was compounded by reactor meltdowns at the Fukushima nuclear power plant, which sent tens of thousands of people fleeing from radiation.

Researchers looked at 178 children whose parents or guardians agreed to cooperate in the three areas that were worst-hit by the catastrophe - Iwate, Miyagi and Fukushima.

They used an internationally recognised child behaviour checklist, and met with children between September 2012 and June last year.

The level of children who need psychiatric care is more than three times that seen in parts of Japan that were not affected by the disaster - for example, 8.5 per cent of children in Mie prefecture in central Japan need help, the study said.

Officials at the Health Ministry and medical organisations involved in the study could not immediately be reached for commenton the report.

"It is known that children need [psychiatric] care right after an earthquake disaster, but this study was done more than a year and half after the fact, so that concerns me," Makiko Okuyama of the National Centre for Child Health and Development, who participated in the study, told Mainichi Shimbun.

AFP