There certainly are some intellectual super-pessimists such as Schopenhauer, Philipp Mainlander, Thomas Ligotti, Emil Cioran, and Peter Zapffe. Buddhism, too, should lead to nihilism, although its practitioners often say that unattachment leads rather to compassion.

How do we know, though, that these ultra-pessimists didn't or don't suffer from depression? Depression would have exactly the same result, a feeling that nothing is worth doing.

In any case, nihilism as a philosophy would entail that nothing has real meaning. Whether anyone can live with nihilism is another matter.