Why does prolonged use of certain antidepressants targeting serotonin reuptake eventually lead to a diminished effect on mood elevation?

💡 Explanation

Prolonged use of selective serotonin reuptake inhibitors (SSRIs) can lead to receptor downregulation, reducing the number of postsynaptic serotonin receptors. This occurs because constant stimulation by elevated serotonin levels causes cells to reduce receptor expression; therefore, the antidepressant effect diminishes over time, rather than from increased neurotransmitter breakdown or permeability changes.

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