Risperidone group
Following the baseline assessment, subjects will enter an open treatment group with Risperidone oral solution(Risperdal) lasting 6 weeks. The subjects will start with a dose of 1ml/d , which would be adjusted to as low as 4 ml/d or as high as 6 ml/d, based on clinical response.Drug dose adjustments interval is generally not less than 2 days, and should reach a effective dose of 4~6ml/d within 1 week.