The purpose of this study is to determine whether the administration of risperidone is effective in the treatment of selective serotonin reuptake inhibitor (SSRI)-resistant post-traumatic stress disorder (PTSD) in civilians.

Individuals with PTSD often experience anxiety attacks, nightmares, or repeated unwanted memories after experiencing or witnessing life-threatening events, such as serious accidents or natural disasters, or traumatic events such as physical or sexual abuse.

Risperidone has been approved by the Food and Drug Administration for the treatment of psychotic disorders and has been found helpful for PTSD and depression, but is still considered investigational for the purposes of this study.

All qualified participants will be started on sertraline (Zoloft) for eight weeks. Patients who are still symptomatic at the end of this phase, will be invited to join the second portion of the study where they will be randomly assigned to receive risperidone or placebo (sugar pill) in addition to the sertraline. Participants will be monitored regularly for medication effects, adverse events, and PTSD symptoms.

Inclusion Criteria:

• Meets criteria for DSM-IV PTSD for a minimum of one month duration
• Clinician-Administered PTSD Scale (CAPS) score > or = to 50
• Able to read and complete questionnaires and interviews
• Negative urine drug screen

Exclusion Criteria:

• Pregnant or nursing
• Primary psychotic disorder; psychotic disorder; or cognitive disorder.
• Prominent suicidal or homicidal ideation
• Alcohol or substance dependence within 3 months of starting study
• Primary anxiety disorder or bipolar disorder
• Patients currently being treated with antipsychotic medication
• Patients in active psychotherapy aimed at PTSD
• Combat-related PTSD