Effect of Psychobiotics With Standard Antiddepressants in Treatment of Major Depressive Disorder

Major depressive disorder (MDD) is a leading cause of disability worldwide, and many patients experience only partial improvement with antidepressant treatment alone. Increasing evidence suggests that the gut-brain axis plays an important role in the pathophysiology of depression. Psychobiotics, including Lactobacillus helveticus and Bifidobacterium longum, may improve depressive symptoms by modulating the gut microbiota, reducing inflammation, and influencing neurochemical pathways.

This study is a randomized, double-blind, placebo-controlled trial designed to evaluate the efficacy and safety of adjunctive psychobiotic therapy in adults with MDD receiving standard antidepressant treatment. Participants will continue their prescribed antidepressant medication and will be randomly assigned to receive either a psychobiotic capsule containing Lactobacillus helveticus and Bifidobacterium longum or a matching placebo once daily for 6 weeks.

Depression severity will be assessed at baseline, Week 3, and Week 6 using validated rating scales. Safety and tolerability will be evaluated through adverse event monitoring, treatment adherence, and regular follow-up visits.

The primary objective is to determine whether adjunctive psychobiotic therapy produces a greater reduction in depressive symptoms compared with placebo. Secondary objectives include evaluating safety, tolerability, treatment adherence, patient satisfaction, and quality of life. The findings will provide evidence on whether psychobiotics are an effective and safe adjunct to antidepressant therapy in adults with major depressive disorder.

Inclusion criteria

• Patients diagnosed with major depressive disorder (According to Diagnostic & Statistical Manual-5 criteria (as per operational definition)
• Age 18 to 60 years
• Both genders
• Patients who are able to speak and understand Urdu/ English language.
• Patients who are on stable doses of oral selective serotonin reuptake inhibitors for at least two weeks prior to enrollment in the study
• Patients with cut off score of > 24 as assessed by 17 item clinician administered Hamilton depression rating scale.

Exclusion criteria

• Severe psychiatric comorbidities (schizophrenia, bipolar disorder, co morbid substance use)

• Individuals with weakened immune systems: This includes patients undergoing chemotherapy, transplant recipients, and people with conditions like HIV/AIDS.
• Individuals on chronic medication: People on chronic pharmacological therapy, especially with anti-inflammatory drugs or who have recently used antibiotics in last 2 weeks.
• Pregnant or lactating women
• Current use of probiotics or prebiotics