This study looks at how probiotics, which are *good bacteria* that help our gut, can help people with Parkinson's Disease (PD) who also have depression. Parkinson's is a brain disorder that causes movement problems and can also lead to depression. The study will last 12 weeks, and participants will either take probiotics or a placebo (a pill with no active ingredient). Probiotics are known to help mood and depression in other people, and this study wants to see if they can help those with PD too.

• The study lasts for 12 weeks, and participants will be split into two groups, probiotic or placebo.
• Participants need to be between 40 and 80 years old and have mild to moderate Parkinson's.
• Regular check-ins and assessments will be conducted, with some blood and stool samples collected.

If you have Parkinson's and mild to moderate depression, you might consider joining this study. It's important to be comfortable with providing samples and attending assessments. Additionally, you should not have used certain medications or probiotics recently and must be able to follow study requirements. Participants will mostly be recruited from a clinic in Vancouver, Canada.