WANG Zhi-ren and TAN Yun-long contributed equally to this work. Correspondence to: ZHOU Dong-feng, Institute of Mental Health, Peking University, Huayuan North Road 53, Haidian District, Beijing 100191, China (Tel: 86-10-82801998. Fax: 86-10-62028350. Email: zhoudf@bjmu.edu.cn); YANG Fu-de, Beijing Hui-Long-Guan Hospital, Beijing 100096, China (Tel: 86-10-62718210. Fax: 86-10-62716285. Email: yangfd200@ 126.com)