Mental illness is not something we often talk about at work, but for those who suffer from a mental illness, it often affects how they go about their day.

That often affects their work — usually, but not always, in a negative way.

New research from Barbara Biasi and Petra Moser at Stanford and Michael S. Dahl at Aalborg University in Denmark shows that to be true for bipolar disorder, which "causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks," according to the National Institute of Health.

People with bipolar disorder usually experience both “manic” (euphoric and optimistic) and depressive states. Because of this, it is sometimes called “CEOs disease.” The characteristics of manic states — things like being optimistic and being willing to take more risks — tend to make good entrepreneurs.

But there is a big catch: There seems to be a barbell-like distribution of success. So if you have bipolar disorder, it’s much more likely that people with bipolar disorder won’t make it to management and will earn less than their peers. But if you are successful, you’re more likely than other people to be super-successful.

Here are the results (emphasis added):

Controlling for year and cohort fixed effects, as well as for other mental disorders, bipolar individuals earn 43 percent less on average. But they are also 8 percent more likely to enter the 90 percentile of the wage distribution and 7 percent more likely to enter the 95 percentile of the wage distribution.

The findings seem to suggest that the people with bipolar disease who are most successful are those who are executives at small firms. They earn, on average, 18% more than the overall population. However, the bump doesn’t trickle down to employees. There isn’t a significant difference between the wages of bipolar employees of small firms and the rest of their colleagues.

And the research suggests that being treated for the disease is very important. The conclusion finds that “access to lithium eliminated the wage penalty for average wages, and it further improves the likelihood that bipolar individuals break into the top percentiles of the wage distribution.”