Schopenhauer refers to the correlation between human intelligence and suffering in The World as Will and Idea. The capacity for abstract thinking, he writes, is a major condition for suffering, because it inflates the suffering beyond the present moment. Suffering merely in the present moment he judges to be, by comparison, much smaller.
The causes of our pain, as of our pleasure, lie for the most part, not in the real present, but merely in abstract thoughts. It is these which are often unbearable to us—inflict torments in comparison with which all the sufferings of the animal world are very small.
(Vol. I §55)
Schopenhauer further derives from this assumption the right of human beings to use animals for labor and to kill them for food. Schopenhauer did advocate for compassion for animals, and for prevention of cruelty towards animals. This is related to the fact that the sentiment of compassion, rather than abstract principles and reason, stands in the center of Schopenhauer’s moral philosophy. Nevertheless, Schopenhauer judged that human beings have the moral right to e.g. kill animals for food, because they, as intelligent beings, are much more prone to suffering than the non rational animals.
The right of man over the life and powers of the brutes rests on the fact that, because with the growing clearness of consciousness suffering increases in like measure; the pain which the brute suffers through death or work is not so great as man would suffer by merely denying himself the flesh, or the powers of the brutes.
As for antecedents, I am not sure about philosophers, but the general idea that intelligence and suffering are correlated, is mentioned already in the Old Testament.
For in much wisdom is much vexation; and he that increaseth knowledge increaseth sorrow.