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Keywords:

  • depression;
  • dopamine;
  • Parkinson;
  • striatum

Abstract

Motor symptoms form the hallmark of Parkinson's disease (PD), although other features such as depression are often present. Currently-used depression rating scales measure affective and somatic symptoms. These somatic symptoms of depression can also be core PD symptoms, suggesting an overlap of symptoms between depression and PD. Using in vivo radiotracer methods, striatal dopaminergic dysfunction is found in both PD and depression. This study investigates to what extent the overlapping symptoms of depression and PD are associated with the striatal dopaminergic dysfunction typical of PD. Symptoms of depression were assessed in 23 PD patients who did not have major depression according to the Montgomery–Åsberg depression rating scale (MADRS; cut-off < 18) and according to a trained psychologist who interviewed all patients. The striatal dopaminergic activity of patients was assessed with FDOPA-PET. Dopaminergic activity of the putamen and caudate nucleus was associated with MADRS total score and specifically with the symptom ‘Concentration difficulties’. These results suggest that the typical striatal dopaminergic dysfunction of PD can cause symptoms that can also be categorized as symptoms of depression. In particular, cognitive symptoms measured with a depression rating scale may be based on the dopaminergic dysfunction of the striatum in PD patients.