Nihilism is still a form of depression.

Things are not permanent, yes. All things arise and pass, including nihilism and depression.

The folks I know who are truly in equanimity and live in the present, are present in the moment, are among the most vibrant and real people I know. When they laugh, they laugh, when they grieve, they grieve. They are fearless in their love, even knowing that all things will pass.