Actually, an extensive study done of 987,308 subjects by the University of Bristol in England found just the opposite to be true. In fact, they found that suicide rates among those with IQs on the lower end of the scale were 2-3 times as high as among those on the upper end.
I don't have a direct link to the study because it was published in the States by Baylor University Media, but the results were released in 2005. The lead researcher was Dr. David Gunnell, Professor of Epidemiology at the University of Bristol. They linked the higher suicide rate to lower IQs at least partly because lower IQ people tend to make poor life decisions, which in turn create greater stress. Higher IQ types tend to be better able to cope with depression because they possess greater problem solving capability.
You really should do a little homework before you post.