Over a million people in the Netherlands use psychotropics, like anti-depressants and anti-psychotics. After use residues enter surface waters, where they are known to affect aquatic organisms. Currently, very limited information is available on the environmental risks. As psychotropics are designed to affect the nervous system, they are also known to affect aquatic organisms at very low and environmentally relevant concentrations and are expected to mimic so-called info-chemicals, influence natural communication and cause effects on the behaviour of organisms. The project aims to assess the effects of psychotropics at the individual, population as well as the ecosystem level, by the use of laboratory, microcosm and mesocosm experiments.