I suspect that this is highly dependent on the person involved and the circumstances that they're in. If someone is manic and has a very low IQ, they are more likely to do silly and hurtful things, but on the other hand if they have a higher IQ and control over their cognitions, mania might not be so bad as the person is less likely to make the same unwise decisions.

On the other hand, during depression the opposite may be true: the person with a higher IQ might feel a deeper sense of despair, while the person with a lower IQ just can't keep their mind off of whatever immediate problem is facing them.

Neither of these suggestions are strict rules, every person is unique, and every situation is unique.