After singing together in a group, people with Parkinson’s don’t show any clear link between how much their movement symptoms improve or worsen and how much their stress hormone (cortisol) changes.

A within-subjects crossover RCT where each person with Parkinson’s disease participates in two sessions: one of group therapeutic singing and one of a matched control activity (e.g., quiet listening), in random order, with at least one week washout. Motor symptoms (UPDRS-III) and cortisol levels (salivary or serum) are measured immediately before and after each session. The primary analysis tests whether the change in UPDRS-III correlates with the change in cortisol across individuals, with correlation coefficients and confidence intervals reported.

A prospective cohort study enrolling persons with Parkinson’s disease who voluntarily attend a single group therapeutic singing session. UPDRS-III and cortisol levels are measured before and immediately after the session. Researchers compute individual-level changes in both variables and perform a Pearson or Spearman correlation analysis to determine if the magnitude of motor symptom change is statistically associated with the magnitude of cortisol change.

A case-control study comparing individuals with Parkinson’s disease who show large changes in UPDRS-III (>10-point improvement/worsening) after singing to those with minimal change (<3-point change). Cortisol changes are compared between these two groups to test whether the direction or magnitude of motor change is linked to cortisol response.

A single-timepoint survey of persons with Parkinson’s disease who recently attended group singing, asking them to recall their perceived motor change and stress level, with cortisol measured once after the session. The study tests whether self-reported motor change correlates with cortisol level at that single timepoint.