The purpose of this research of 400 participants is to determine whether a drug called risperidone can decrease symptoms of Post-Traumatic Stress Disorder (PTSD). It is a placebo-controlled study, meaning that half of the participants will be assigned to receive a pill that contains no drug. The treatment phase of the study will last for 6 months, during which time participants will continue to receive all their usual treatments in addition to the study treatment and will be asked to complete procedures and assessments (questionnaires, interviews, laboratory tests, physical exams, etc.) related to their PTSD symptoms at various points within the 6-month treatment phase. At the end of the 6-month study, participants will discontinue the study treatment.

Primary Hypothesis: Risperidone will reduce symptoms of PTSD, relative to placebo, in veterans with military service related chronic PTSD who have been partial or non-responders to antidepressant medications.

Secondary Hypothesis: Risperidone is safe and well-tolerated in veterans with military service related chronic PTSD, and patients will comply with its prescription. As a result, patients will show improvement in the secondary consequences of PTSD for the veteran and for the VA.

Intervention: Usual (PTSD) care plus Risperidone vs usual (PTSD) care plus placebo Study Abstract: Four hundred veterans with the diagnosis of military-related PTSD will be enrolled at 20 VAMC hospitals over a two-year period. An equipoise stratification design will be used to randomize patients in a double-blind manner to risperidone or placebo (~200 patients in each group) for six months of treatment. Usual care will be provided for all patients for treatment of PTSD and other psychiatric and medical disorders. Comparisons between the risperidone and placebo groups will be made at the end of six months to answer the primary question. The sample size is calculated to give 90% power at the two-sided alpha level of 0.05 for the overall test for the CAPS score change.

STUDY UPDATE/NOTES: The study kicked-off in late July 2006 with recruitment expected to begin October 1, 2006.

Oct2006 - Participating sites are seeking approval for the protocol amendment which resulted from the Kick-Off meeting. Patient recruitment at each site will begin as soon as they receive approval of the amendment.

• Drug: Risperidone
• Drug: Placbo

• Active Comparator: PTSD
• Placebo Comparator: PTSD

Inclusion Criteria:

• 18 years or older
• Military service related chronic PTSD
• CAPS score >50
• Participant in VA outpatient PTSD clinic
• History of non-response to two or more antidepressants

Exclusion Criteria:

• Comorbid Axis I diagnosis requiring antipsychotic medication
• Substance dependence diagnosis (excluding nicotine)
• Hepatic or renal problems
• Incompatible medical diagnosis or medication (i.e., coumadin, insulin)
• Unstable living arrangements
• Assault or suicide gesture within 1 year