The Efficacy of Probiotic Compared With Placebo Commitment Therapy for Treatment of Major Depressive Disorder

Inclusion Criteria: * Female patient diagnosed with major depressive disorder (confirmed by DSM-5 for depression). There is a strong gender predisposition in depression and anxiety disorders, in which females are more prone to have depressive disorders and anxiety disorders than males. Hence, we will only recruit female patients in this study to control for confounding bias. * Those with score of more than 8 based on Hamilton Depression Rating Scale (HAMD), indicative of mild to moderate severity of depressive symptoms. * Age 18 to 35 years old Exclusion Criteria: * Pregnant women * Those who have current and lifetime history of engaging in any psychotherapy * Those who consumed alcohol and illicit drugs (Heavy or mild) * Those who has current and lifetime history of other psychiatric illnesses, such as other depressive disorders (persistent depressive disorder, premenstrual dysphoric disorder), anxiety disorders (panic disorder, agoraphobia, generalized anxiety disorder, specific anxiety disorder, and social anxiety disorder), psychotic disorders (schizophrenia, schizophreniform disorder, schizoaffective disorders, brief psychotic disorder, and delusional disorder), bipolar mood disorder, obsessive compulsive disorder, posttraumatic stress disorder, and attention deficit hyperactive disorder, and autism spectrum disorder * Those who are on medications that can induce psychiatric symptoms, such as cardiovascular agents (clonidine, guanethidine, methyldopa, reserpine, beta blockers), dermatologic agents (isotretinoin), anticonvulsants (levetiracetam), antimigraine medications (triptans), hormonal agents (corticosteroids, oral contraceptives, gonadotropin-releasing hormone agonists, tamoxifen), varenicline, immunological agents (interferons), and levodopa * Severe gastritis with regular intake omeprazole medication (proton pump inhibitors) * Women on regular steroid treatment * Those on long term medication for any illnesses (≥ 6 months) * Those who are currently on antibiotics or with history of taking antibiotic for the past 2 weeks. * Those with abnormal full blood count, renal profile, liver function test, fasting blood glucose, fasting lipid profile and ESR (blood collection for all these blood investigations will be carried out in the pre-intervention assessment). * Patient who has suicidal tendency