How Shrimps are Doped Up on Prozac

Antidepressants are leaking into our waterways, and we may be unknowingly taking them.

Written by: Ornrumpa Amornkasemwong

Edited by: Nitya Mahajan

Art by: Cecilia Mou


“Our aquatic life is bathing in a soup of antidepressants,” says Professor Alex Ford, a marine biologist at the Institute of Marine Biology, University of Portsmouth.

Traces of antidepressants like fluoxetine (commonly known by its trade name “Prozac”) are found in streams and soil, and reports are indicating that these contaminants are accumulating in non-target animals that live in those environments. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) that eases depression by blocking the reabsorption of serotonin. A study published in Water Research reported that high concentrations of such drugs are detectable in densely populated areas — noticeably in the River Thames near London’s Houses of Parliament.

Like many drugs, antidepressants are not fully metabolised in our bodies and are discharged through urine to wastewater treatment plants. These treatment units, however, are not capable of breaking down drugs, so they end up infiltrating our rivers and estuaries. With the growing number of people with mental health problems and use of antidepressants (which has more than doubled in the last decade just within the UK), the problem of water contamination is expected to worsen.

While it’s been established that residues from therapeutic drugs can end up in the aquatic environment, the implications and downstream effects of these drugs on wildlife species are yet to be studied.

The Effects

To figure out how drug pollution is affecting aquatic life, Guler and Ford exposed amphipods, which are an important constituent of marine and freshwater ecosystems, in water containing antidepressants about the same amount as that found in some sea water. Using infrared cameras and a tracking software to measure their behaviours and activities in the dark, they noticed that the organisms’ phototaxis and geotaxis behaviours altered significantly in a concentration-dependent manner. Fluoxetine, in particular, demonstrated to significantly alter phototaxis and geotaxis activity. Amphipods exhibited increased ventilation at relatively low fluoxetine concentrations, and increased locomotion at higher concentrations. Additionally, they appeared to leave their natural habitat more often, quintupling their time spent in the light.

Phototaxis and geotaxis behaviours underline the organisms’ survivability. Changes to these behavioural patterns have ecological implications, as it means that the organisms are not capable of effectively responding to predators, leading to detrimental effects on the population dynamics. Other species, such as birds that forage on invertebrates at wastewater treatment plants, are also exposed to these pharmaceuticals. To better understand the implications of exposure, Whitlock and her colleagues studied wild-caught starlings (Sturnus vulgaris), a species commonly found near wastewater treatment plants.

Behavioural changes, particularly courtship behaviours, were examined. Male starlings sang less and became more aggressive towards fluoxetine-treated females rather than to control them. Research suggests that antidepressants in the environment are altering fitness-related traits in wildlife — potentially harming the ecosystem.

Addressing the Problem

Drug pollution doesn’t only affect the animals and plants that live in that water, but also the life on land that depends on that water for survival. Contaminated water sources can cause diseases, and even death. It can also have severe economic impacts, as many people depend on waterways as a source of food and income. Moreover, such pollution discourages water-based recreation, which coastal communities depend on to make a living. One suggestion towards addressing the problem is by upgrading the UK’s wastewater treatment plants so that the contaminants’ concentration is reduced to an acceptable level.

On the prescription side, incentivising and educating people on how to safely dispose unused or expired drugs, such as returning them to pharmacy, can avoid them being flushed down or thrown into landfills. Psychological counselling, on the other hand, should also be made more affordable and accessible to patients so that prescription of antidepressants can be reduced.

Before the problem of water contamination worsens any further, we must start considering these approaches and adopting practices that would prevent drugs from entering our waterways. Failing to do so may pose risks not only to the aquatic life, but to us as well. It may seem difficult, but it’s crucial that we start trying now.

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