Upon completion of a screening assessment subjects will begin treatment with desvenlafaxine. For subjects who are currently prescribed an alternate SSRI or SNRI, they will be titrated off their current medication and begin desvenlafaxine, according to the clinical judgment of the investigator based on proven best practices. All subjects will begin on a dose of 50 mg of desvenlafaxine and after 4 weeks of active treatment may be titrated up to 100 mg daily. At the 8-week visit, individuals assessed as partial-responders, in the judgment of the investigator, may be titrated up to 150 mg daily. Personal clinical experience of the principal investigator has shown desvenlafaxine can be safely increased above a dose of 100 mg daily in partially responsive patients. The decision to titrate is based on a risk benefit analysis, as 150 mg is shown to be effective with limited side effects in younger patient populations. The principal investigator is comfortable with a daily dosage of 150mg and will assess for potential side effects. Blood pressure will be monitored at baseline and every 4 weeks as there is evidence that an increase in these values is more likely with dose escalation. It is estimated that 5-15% of the 30 patients may require 150 mg of desvenlafaxine as partial or non-responders to 100 mg daily. Patients prescribed 150mg desvenlafaxine and requiring downward titration will move to 100mg/d for 7 days, then 50mg/d for 7 days, followed by 50mg every other day for 7 days before discontinuation. Patients prescribed 50mg/d or 100mg/d will undergo similar downward titration prior to study drug discontinuation.