Which medical condition must precede the onset of Major or Mild NCD in cases due to Parkinson's Disease?

The correct response emphasizes that an established clinical diagnosis of Parkinson’s Disease is necessary for confirming cases of Major or Mild Neurocognitive Disorder (NCD) stemming from this illness. Parkinson’s Disease is a progressive neurological condition characterized by motor symptoms such as tremors, rigidity, and bradykinesia, and is also associated with cognitive decline that can lead to NCD.

In the context of NCD related to Parkinson’s, the cognitive symptoms and impairment in functioning arise as a direct consequence of the underlying pathophysiological changes in the brain due to Parkinson's. Therefore, a definitive diagnosis of Parkinson’s must be established before determining if a neurocognitive disorder is present. This requirement ensures that the diagnosis of NCD is correctly linked to the direct effects of Parkinson’s as opposed to other factors that might not be connected to the disease itself.

Considering the other options, multiple medical conditions do not specifically indicate a singular causative relationship necessary for the diagnosis of NCD related to Parkinson’s. Neurocognitive symptoms may arise from various sources and do not necessarily precede the diagnosis of Parkinson’s. Similarly, substance use disorders may contribute to cognitive decline but are not inherently required for a diagnosis of NCD due to Parkinson's. Thus, the presence