A prospective, randomized, active–controlled, parallel–group comparative open label study will be conducted on total 92 patients of major depressive disorder at psychiatry OPD, meeting inclusion criteria, after permission of Institutional ethics committee. Prior permission from head of department of pharmacology, psychiatry, pathology, biochemistry, will be taken. Registration to clinical trial registry (CTRI) will be done.  GCP guidelines will be strictly followed.

Diagnosis of patient as a patient of major depressive disorder will be done by psychiatrist. A written informed consent from the patient or legal guardian of patient will be taken after explaining nature and purpose of study in their own language. Patient information sheet containing all the necessary details of study will be provided to patient. Eligible patients will be randomized using block permutation method with allocation ratio of 1:1 to receive either escitalopram or vilazodone.

Patient’s details will be taken on a proforma, including patients age ,sex, occupation , religion, marital status ,type of family , total family members , total income, per capita income, socio -economic class (by B.G. Prasad classification) ,history of  any medical illness , duration and treatment received for the same will be recorded.  Family h/o any psychiatric disorder will also be taken. Also patient’s weight, BP, will be recorded. Weight of patient will be taken on a same type digital weighing machine throughout the study. BP of patient will be recorded with same type of sphygmomanometer till the end of study. CBC, serum creatinine, serum urea, liver function tests will be done, at baseline (day 1), 4^thweek, and at 12 weeks at the same institution with same method.

Before starting treatment, baseline(day 1)Hamilton depression rating scale  (HAM- D),Hamilton anxiety  rating scale (HAM –A) ,Montgomery –Asberg Depression rating scale (MADRS), clinical global impression- severity (CGI-S) score will be taken, also baseline(day 1)  blood investigations such as CBS, LFT ,RFT will be done after which  treatment with either  vilazodone (10mg ) or Escitalopram(5mg) orally as prescribed by psychiatrist will be started. Patient will be advised to take vilazodone with food. Dose of the drug will be doubled every week maximum upto 40 mg for vilazodone and for escitalopram dose will be increased by 5mg every week maximum upto 20mg if inadequate response is obtained .

Subsequent  follow -up will be taken at 1^st , 2^nd ,4 ^th and 12^th week and changes in the HAM –D , HAM–A, MADRS , clinical global impression improvement (CGI –I) and clinical global impression severity (CGI-S) Score will be recorded. Follow up blood investigation will be done at 4^th and 12^th week. The primary efficacy outcomes will be taken as change from the baseline in the values of HAM-D₁₇ total score (change from baseline to last post baseline assessment).secondary outcome measurers will be HAM –A, MADRS and CGI-I, CGI–S score, total 50% reduction in scores will be considered as response to therapy.