Home and work stress can take heavy mental toll, specialist says

"Sometimes, I would sit in my lab staring at the equipment and ask myself over and over again, 'Why am I alive?' "

This is how PhD student Sun, 27, who did not want his full identity revealed, recalls one of his lowest points. "It was a few years ago, but at the time I just couldn't see a future," he said. "I still can't, I guess."