This subject has been discussed by colleagues and expats on forums for the last few years (that I've paid attention to). I've heard many stories of teachers who have taught students who committed suicide. I've been fortunate enough that all of my students were accounted for throughout the time I taught.
The statistics aren't good for China. According to the WHO the suicide rate in 2003 was 13 per 100,000 for men and 14.8 per 100,000 for women. This does not include Hong Kong, which also has a high suicide rate. Only Lithuania and Sri Lanka had a higher rate for women. An article on Asiaone from year ago claims that China has between 250,000 and 300,000 suicides per year.
I've heard a lot of talk about improving mental health services around the country, but I haven't seen any evidence. I hope stories like this force the government to put money into mental health services for everyone in China.