Ah Kei is one of 33 socially withdrawn teenagers aged from 15 to 24 involved in a two-year 'Regain Momentum' programme - sponsored by the Bank of China - which the centre started last September. He sought help from the centre in 2009 and got involved in pet-related activities such as an animal grooming course.

Helen Pong, who owns 10-year-old golden retriever 'dog doctor' Cha Cha, said she saw a change in the youth at the centre. 'At first they were afraid of this huge dog, but as time goes by, they make friends and - to their delight - he recognises them ... They're happier, and everyone here is getting more involved,' she said.

Socially withdrawn teenagers, or 'hermit youth', are unemployed school drop-outs who refuse to leave their homes for long periods to avoid social interaction with others.

The 33 cases are among 200 being handled by the centre - a third of them reclusive teenagers. They were reported to the centre by their parents or social workers from other community centres.

'Our programme pursues a step-by-step re-engagement of these alienated young people. You can't expect them to find a job just a few days after the therapy. But at least they are now willing to get out of the house and come to the centre to play with the dogs,' Henry Ng Yan-ho, general secretary of the social service centre, said. 'All we need is patience.'

He said the therapy helped to reduce feelings of loneliness, provided a sense of closeness and security, building positive self-image and improving interpersonal skills.

Dr William Fan Tak-wing, psychiatry specialist and chairman of the Hong Kong Animal Therapy Foundation, said: 'Animal-assisted therapy is not a panacea for the problem. But it can help more reclusive adolescents than other therapies as they don't feel like there's something wrong with them - it's more like something for leisure or relaxation.'