system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: People get Parkinson disease due to loss of Dopamine, Since Dopamine also controls the reward system of the brain, so does that mean that people with Parkinson disease are usually sad and depressed?
gpt
> People get Parkinson disease due to loss of Dopamine

That's not true. There's a *correlation* between the two, but we don't know it's the cause. It might be that whatever causes Parkinson's *also* causes the damage to dopamine receptors. 

Also, depression is linked to serotonin and norepinephrine, not dopamine. If anything, there'd be a lack of *motivation*, not depression.