Probiotic Administration for Adolescent Depression

Inclusion Criteria:

• Female and male participants 15 to 24 years of age

• Fluency in English

• Access to smartphone, tablet, or computer, on which program "Zoom" can be run forremote visits

• Diagnosed with a primary DSM-5 clinical depressive disorder (Major DepressiveDisorder, Persistent Depressive Disorder, or Other Specified Depressive Disorder).The DSM-5 clinical depressive disorder will be confirmed by the Schedule forAffective Disorders and Schizophrenia for School-Aged Children-Computerized Version (K-SADS-COMP)47 to participants <18 years and the Structured Clinic Interview forDSM-5 (SCID-V) to participants ≥18 years.

• Participants must be under the care of a primary care clinician and/or mental healthprofessional

• Currently on SSRI for at least 8 weeks

• BDI-II score greater than 13

Exclusion Criteria:

• Current diagnosis of other DSM-5 mental health disorders except for anxietydisorders and ADHD as long as depressive disorder is the primary diagnosis

• Current medically-treated with stimulant medication for ADHD unless subject is onstable dosage of stimulant medication and there are no plans to change the stimulantmedication or dosage for at least 8 weeks.

• Current diagnosis of any Axis II personality disorder(s) as assessed by theK-SADS-COMP or SCID-V.

• Oral probiotic use 1 month prior to phone screening

• Oral or IV antibiotic use 1 month prior to phone screening

• Fermented foods (e.g., yogurt, kombucha) 1 month prior to phone screening

• Oral antioxidant or omega 3 supplements <6 weeks prior to phone screening

• Current alcohol intake greater than 2 drinks per week

• Smoking cigarettes (>5 during last 6 months) or tobacco (pipe or hookah #1 timeduring last month)

• Any plans to make significant change in diet and lifestyle

• Immunocompromised patients

• Allergies to milk, soy, or yeast

• Tanner Stage <3

• Current active suicidal ideation that requires psychiatric hospitalization orsuicidal ideation with plan or intent to attempt suicide as assessed by theColumbia-Suicide Severity Rating Scale (C-SSRS)

• Prior suicide attempt within past 6 months that required hospitalization and/orvisit to the Emergency Department

• History of failure to clinically respond to 2 or more adequate trials of 2 differentfirst-line SSRI antidepressant medications

• Any contraindication to MRI (e.g., braces)

• Pregnancy or any plans to become pregnant during the study is an exclusion criterionfor entrance into the study. Women of reproductive capability will be asked aboutpregnancy or plans to become pregnant. Women of reproductive capability will beasked to employ at least one of the following allowable contraception methods untilthey complete their second MRI: birth control implant, birth control shot, birthcontrol patch, birth control pill, condom, internal condom, birth control sponge,cervical cap, spermicide, fertility awareness (calendar method), outercourse andabstinence.