The effects of antidepressants appear to be rapid and at environmentally relevant concentrations.

The effects of antidepressants on wildlife are currently raising some concern because of an increased number of publications indicating biological effects at environmentally relevant concentrations (<100 ng/L). These results have been met with some scepticism because of the higher concentrations required to detect effects in some species and the perceived slowness to therapeutic effects recorded in humans and other vertebrates. Because their mode of action is thought to be by modulation of the neurotransmitters serotonin, dopamine, and norepinephrine, aquatic invertebrates that possess transporters and receptors sensitive to activation by these pharmaceuticals are potentially affected by them. The authors highlight studies on the effects of antidepressants, particularly on crustacean and molluskan groups, showing that they are susceptible to a wide variety of neuroendocrine disruptions at environmentally relevant concentrations. Interestingly, some effects observed in these species can be observed within minutes to hours of exposure. For example, exposure of amphipod crustaceans to several selective serotonin reuptake inhibitors can invoke changes in swimming behavior within hours. In mollusks, exposure to selective serotonin reuptake inhibitors can induce spawning in male and female mussels and foot detachment in snails within minutes of exposure. In the light of new studies indicating effects on the human brain from selective serotonin reuptake inhibitors using magnetic resonance imaging scans, the authors discuss possible reasons for the discrepancy in former results in relation to the read-across hypothesis, variation in biomarkers used, modes of uptake, phylogenetic distance, and the affinity to different targets and differential sensitivity to receptors.