Stockholm University Jun 8 2026 A new study has uncovered how antidepressants affect different groups of serotonin-producing brain cells in opposite ways, offering new insights into why selective serotonin reuptake inhibitors (SSRIs) can cause unpleasant side effects at the start of treatment but lead to symptom relief over time. Antidepressants are among the most widely prescribed medications in the world. In Sweden, more than one in ten people currently use an antidepressant, and SSRIs are by