A new study published in the Journal of the American Medical Association shows that anti-psychotic drugs like Risperdal do not help alleviate PTSD symptoms, despite their common use with veterans.
According to the study, 20% of veterans being treated by the VA for PTSD took an anti-psychotic in 2009. More than 90% of those veterans took second-generation anti-psychotics, which include Risperdal.
The FDA has not approved the use of anti-psychotics for treatment of PTSD.
You can read more about the study here, and find the actual study here. (The paper is free right now, but may be behind a pay firewall later.)