Hong Kong counsellors went undercover among Japan quake survivors to discover how they had been affected by the ordeal.
Timothy To Wing-ching, executive director of the Post Crisis Counselling Network, said helpers were warned that people in northeast Japan - the area worst-hit by the disaster - were quite shy.
So instead of approaching them directly, they tried to win their confidence by other means before starting the real work of identifying those suffering from post-traumatic stress disorder.
'We pretended we needed their help,' To said. 'Volunteers jogged near their shelter in the hope of meeting them, and sometimes asked where the toilet was or what a Japanese word meant.'
Of 99 survivors the team assessed at a hotel used as a temporary shelter in the city of Hanamaki in Iwate prefecture, about a third had the disorder, which can cause sleeplessness and delusions.
Most of the people they met were elderly fishing people or farmers.