Mirtazapine does not have serotonergic activity and does not cause serotonergic side effects or serotonin syndrome.[65][64] This is in accordance with the fact that it is not a serotonin reuptake inhibitor or monoamine oxidase inhibitor (MAOI), nor a serotonin receptor agonist.[65][64] There are no reports of serotonin syndrome in association with mirtazapine alone, and mirtazapine has not been found to cause serotonin syndrome in overdose.[65][64][100] However, there are a handful of case reports of serotonin syndrome occurring with mirtazapine in combination with serotonergic drugs like SSRIs, although such reports are very rare, and do not necessarily implicate mirtazapine as causative.[65][101][102][103]