Swedish scholars explored the long-term risk of Parkinson’s disease (PD) in patients after depression and showed that there is a direct correlation between depression and the development of PD. The association between depression and PD remained significant over 20 years of follow-up. This result suggests that depression may be a very early symptom of PD or a risk factor for the development of PD. A related paper was recently published in the journal Neurology. The cohort study included 140,688 depressed patients in a 1:3 ratio with a nested case-control design to assess the current study parameters. Potential familial copulas for both diagnoses were investigated in a subcohort of 540811 sibling pairs. Correlations between the two were analyzed using multivariate corrected statistical models. Results showed that a total of 3260 subjects in the cohort population were diagnosed with PD between a median follow-up time of 6.8 years (1 and 26.0 years). the multivariate corrected ratio (OR) for PD was 3.2 after year 1 of depression and decreased to 1.5 after 15 to 25 years of depression. Among depressed subjects, repeated hospitalizations were an independent risk factor for the development of PD (OR 1.4) . Family analysis showed that sibling depression was not associated with the risk of PD (OR 1.1).