Bodily inflammation dampens levels of a "feel-good molecule" and antidepressants' ability to boost them, according to new research in mice. The findings add to mounting evidence that inflammation, and the accompanying release of the molecule histamine, affects a key molecule responsible for mood in the brain—serotonin. If replicated in humans, the findings—which identify histamine as a "new molecule of interest" in depression—could open new avenues for treating depression, which is the most common mental health problem worldwide. Inflammation—a blanket term describing an immune response—triggers the release of histamine in the body. This increases blood flow to affected areas to flood...