The obituary for William Hurt in The Week mentioned that he suffered from logorrhoea.

It is: Elated or irritable mood, disinhibition and recklessness (social, sexual, financial), pressured speech, flight of ideas (rapidly jumping between tenuously related topics), grandiose delusions, and mood-congruent auditory hallucinations indicate an acute manic episode.

That sounds like manic depressive behaviour without the depression.