Scientists have uncovered new evidence that serotonin, a brain chemical that regulates moods, also plays a role in sudden infant death syndrome. Researchers already had suspicions that serotonin imbalance might contribute to SIDS, but they weren’t sure how it could kill. Now researchers in Italy have engineered mice born with serotonin that goes haywire, and have found the brain abnormality is enough to spur sudden death. The Associated Press reports that this new research, published in the journal Science, suggests that one day it might be possible to test newborns for SIDS risk.