10. Concomitant medications: All medications for pre existing medical conditions will be permitted to continue unchanged provided subjects are on a stable dose of at least 12 weeks. Subjects on concomitant mood stabilizers or atypical antipsychotics will require a 2-week washout prior to screening visit. Subjects on a minimum of 3 month of stable dose of hypnotics (e.g. zolpidem 10 mg per day or benzodiazepine dose of ≤ 2 mg per day of lorazepam or trazodone ≤ 100 mg per day or quetiapine ≤ 100 mg per day) will be allowed to continue their hypnotic medication at the same dose. Quetiapine at doses ≤ 100 mg per day is appropriate only for hypnotic effects. Over the counter medications will be permitted if in the opinion of the investigator, they are not considered to have any significant impact on the study. Any medication that has the potential to cause a clinical significant drug interaction with vilazodone in the judgment of the investigator will require a washout.