What could come of someone w manic depression leaving it untreated?

Bipolar: Serious manic depression could lead to severe problems including high risk of suicide.

Nothing good.: Untreated bipolar disorder is highly recurrent and considered to have a poor prognosis. the interval between episodes tend to shorten with time. Full recovery without further episodes is very rare, and the likelihood of increasing chronicity is great. Without treatment worsening symptoms including an increased risk of suicide would be a major concern.

Myths/Truths: Many highly creative people (in the arts, finance, the sciences) have suffered from manic depression--without treatment--and paid a very high cost. A common myth is that treatment eliminates creativity. This is not so: treatment balances ebullience and constraint, enhancing creative production. Without treatment the condition worsens and has a very high rate of life decline and suicide.

Bipolar: In a worst case scenario, the person could die, either by their own hand or because of extreme/psychotic behaviors while manic. Undiagnosed, unmedicated, and untreated bipolar disorder can tear families apart and destroy marriages. As an aside, the correct modern term for manic depression is bipolar disorder.