Parkinson's disease (PD) is a complex condition that carries a high burden of neuropsychiatric comorbidities. About a third of individuals living with Parkinson's disease have one or more depressive disorders, resulting in lower quality of life, greater care dependency, and increased caregiver burden. Gastrointestinal dysfunction is very common in Parkinson's. Constipation is experienced by the vast majority of patients and often manifests years before onset of motor symptoms, symptoms suggestive of irritable bowel syndrome are also commonly found in PD. Increased intestinal permeability has been demonstrated in PD. Impaired intestinal barrier function can lead to chronic systemic low-grade inflammation, which has been strongly associated with mood disorders. Several lines of evidence suggest a link between the gut microbiome and Parkinson's disease.~The microbiome has been linked to depression both in human and animal studies. Several studies have found beneficial effects of probiotics on mood disorders in non-PD populations, including stress and depressive behaviour in animal models, and sad mood reactivity and major depressive disorder in humans.~In summary, given the high rate of depression in PD, the growing evidence that probiotics may improve depression and mood disorders in non-PD populations, and the strong links between the gut microbiome and PD, we will carry out a randomized, blinded, placebo-controlled study into the use of a multi-strain probiotic to improve depression and Parkinson's disease.~Recruitment: Approximately 60 participants will be randomized to either the probiotic intervention arm or placebo treatment. Participants will mainly be recruited from the Pacific Parkinson's Research Centre movement disorder clinic at the University of British Columbia in Vancouver.~Participants will receive a detailed description of the study and will need to provide informed consent for participation in the study. Participants will be screened for inclusion and exclusion criteria.~Assessments: Clinical assessments of motor function, cognition and neuropsychiatric symptoms will be done before the 12 week intervention phase as well as following after the 12 week intervention with regular check ins during the course of the intervention. Blood samples and stool samples will be collected before and after the intervention. An optional fMRI scan will be completed at the first and last study visit, pre- and post-intervention.~The primary outcome will be the difference between the probiotic vs. placebo groups in mean Inventory of Depressive Symptomatology - Clinician-Rated (IDS-C) pre-/post-intervention. The primary analysis will be based on intention-to-treat. For other secondary outcomes, the between-group difference analysis will be applied to the fatigue, anxiety, PD motor function, severity (UPDRS I-III) and quality of life scores pre/post intervention, respectively. Adverse events, tolerability and drop-out rates will be registered and overall rates compared between the intervention groups. Furthermore, differences and changes in blood markers and microbiome composition will be assessed.
This study evaluates the use of an oral multi-strain probiotic in the treatment of depression in individuals with Parkinson's Disease. Participants will be randomized to either 12-week multi-strain probiotic treatment or placebo with an optional fMRI scan.