Robin Williams Was In Early Stages of Parkinson’s Disease, Says Wife

[cleduc]

7. I think Robin lived with a mood disorder much of his life

Bipolar hypomania. I posted about that here:
http://www.democraticunderground.com/?com=view_post&forum=1002&pid=5377206
and here:
http://www.democraticunderground.com/?com=view_post&forum=1002&pid=5381825

Parkinson's on it's own can bring on mood disorders like anxiety and clinical depression.

Both affect dopamine levels.

Mix a bipolar depression with a clinical depression brought on by Parkinson's and it's not hard to imagine how one might get to feeling pretty low.

I happened to look this up:
Bipolar Affective Disorder and Parkinson’s Disease
http://www.hindawi.com/journals/crim/2011/154165/

Accepted 19 October 2011

Little is known about comorbidities of bipolar disorder such as Parkinson’s disease. A case history and a literature survey indicate that bipolar disorder is linked with or influences Parkinson’s disease and vice versa. Underlying mechanisms are poorly understood, and, more importantly, no treatment options are established in such double diagnoses.
...
In all cases manic or hypomanic episodes had already appeared before the onset of Parkinson’s disease and, furthermore, the authors supposed that Parkinson’s disease accelerates the frequency of episodes.
...
For the special case—the combination of Parkinson’s and bipolar disorder—no specific data for treatment options exist.
...
In conclusion, too little is known about treatment options in bipolar patients with comorbid disease. Further investigations are needed.

and this:
Bipolar affective disorder and Parkinson's disease: a rare, insidious and often unrecognized association.
http://www.ncbi.nlm.nih.gov/pubmed/12548347

and this:
Medial forebrain bundle stimulation as a pathophysiological mechanism for hypomania in subthalamic nucleus deep brain stimulation for Parkinson's disease.
http://www.ncbi.nlm.nih.gov/pubmed/19487890
and there are more like the above

Again, in my opinion, before his Parkinson's diagnosis, Robin was already living in a semi delicate bipolar hypomania condition for decades.

From the quoted articles above, one these things or a combination of them may have taken place:
1) the combination of the periodic bipolar depression with the clinical Parkinson's depression drove him into a very deep depression
2) the medication or treatment to slow or manage Parkinson's could exacerbate his bipolar condition or dull his hypomania such that he could no longer do what he did in comedy and from that, no longer make folks laugh or create his art

The doctors may have told him he was basically screwed and they couldn't help him as much as he felt he needed or they tried what medications/treatment they could and proved it was not going to work. If they concluded he couldn't make folks smile any more, then Robin may have concluded surviving the bouts of deep depression he done much of his life wasn't worth it any more - as there would no longer be much payback for going through that agony. Going forward, he may have forecast he was just going to be a burden on others.

Robin was a very bright and very knowledgeable man - very in tune with science and medicine and in a great position to obtain good medical answers. Maybe something like the above is what he'd concluded or experienced.