Having a high IQ can be very beneficial in many facets of life. However, a common trait found amongst people with high IQ's is the need to perfect everything. While this is not necessarily a bad thing, as aiming for perfect scores on tests is a good goal, it can have tendency to eventually turn unhealthy in these individuals. Perfectionism in gifted individuals is common due to the fact that those individuals are very successful in a lot of the things they do. If this need to be perfect gets out of hand, the gifted individual with a high IQ can develop issues that are unhealthy. One is that in the course of trying to perfect everything, they will eventually run into trouble in that no one, or thing is completely perfect. This will mean that the individual will never be successful if they search for a "perfect relationship". These individuals also have problems setting realistic goals for themselves later in life. If a child easily gets 100%'s on his/her school work, it will be harder for them to set realistic goals in the workplace later in life.
Related to the feelings associated with the inability to achieve perfection is depression. It is possible that the prevalence of depression in gifted people with high IQ is related to this unhealthy perfectionism. I think that maybe if these gifted people are taught early in life that things don't have to be perfect all the time, and that goals should be set reasonably, that maybe the level of depression in gifted individuals could decrease, since they will not be as disappointed in themselves and in the fact that the world is full of imperfections out of their control.