The Hong Kong Christian Service (HKCS) based the estimate on a study of 192 cases it handled and a survey of secondary schools last year. The 18,500 young hermits, some as young as 12, account for 2 percent of the city's youth population. And it tripled HKCS' estimate in 2005.

HKCS said that sufferers often feel unable to face the intense competition in society and escape to their own rooms. The case study also found that parents are often too reluctant to praise their children.

(Wen Wei Po)