▲ Mania Linked To High IQ ▼

From a PhysOrg blog post on bi-polar:

The findings of a link between the disorder and academic and intellectual performance may explain the association between genius and mania that has long been thought to exist. People with bipolar disorder who are in a manic phase can have exaggerated emotional responses and can be witty, inventive and have high cognitive capabilities. They are also capable of sustained concentration and have high stamina, and so can achieve much more than people without the disorder.

In an earlier post, I point out one theory about the evolutionary fitness of bi-polar:

During periods when the optimal response is to be risk prone [that is, during "good" or "dire" circumstances], members of a population need to pursue such risk. If a minority of the population has excessive sensitivity and reactivity to the opportunity to take risk, then such behavior would both be selected for and also biologically fit for the population. This statement could well describe individuals who are episodically manic (bi-polar).

So add to the sensitivity to take significant risk at appropriate times, the likelihood that a state of mania increases cognitive capabilities and stamina: high functioning during periods of significant risk. Bi-polar risk taking might have a low incident of success but high reward when successful, providing both fitness for the condition and high value to society during moments of "good" or "dire" circumstances.