What does it mean that unbelief is the root of depression?

Unbelief is considered the root of depression because it signifies a lack of trust in God's character and promises. When believers are consumed by the world and their own failings, as highlighted in the sermon, they lose sight of God’s assurances. This is reflected in David's struggles, as he repeatedly calls himself to reflect on his hope in God. Overvaluing worldly concerns and neglecting God's promises results in spiritual and emotional distress, underscoring the necessity of faith in sustaining mental health and hope amid life's challenges.