PBS did a television documentary on PBA recently. If you do a search on google under
"pba healthy bodies healthy minds" you should be able to find a link to it.

The MS association, Stroke organization and Brain injury association all did recent surveys on this as well and have them posted on their respective websites. The MS survey in particular was very large and quite surprising.
Out of about 5200 people surveyed they found that 48% of them likely have PBA.

What these sources will show is that what is generally understood to be going on is that in all these illnesses and others as well, a type of lessions or scarring is taking place in the brain in the pathway controlling emotions.
And so, while many seem to brush it off as just being overly emotional, there's a real medical reason for this to be taking place. And, it's just been under diagnosed and written off for years because there was no effective treatment for it. Nuedexta does seem to help it for a great many patients though as you're experieincing yourself.

In any event, wanted to share that information with you and others.

Best of luck to you.