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The Environmental Trade-offs of Increased Antidepressant Use

     I came across an interesting sentiment the other day. In response to the generational expression  “kids have it so easy nowadays” someone replied “that’s the point”. The point of progressing is to make life easier for the next generation. While today’s kids don’t have to walk uphill both ways to get to school, they face their own unique obstacles with the constant pressures from social media and threat of school shootings. The 2021 State Of Mental Health In America survey reports that youth depression is worsening. Statistics show that this disproportionately affects youths who identify as more than one race. However, some statistical growth can be attributed to an increase in diagnoses as the stigma of mental health has changed and more people seek treatment. Along with better access to therapy, access to a variety of antidepressants has increased as well. The CDC reports that from 1999 to 2014 antidepressant use has increased by almost 65% with one in eight Americans over 12 haven taken antidepressants between 2011 and 2014. While this can be considered an improvement in mental health treatment in response to increased rates of depression, ecotoxicologists are becoming aware of the negative environmental effects attributed to an increase in antidepressant use. 

Scientific American reports that only half of pharmaceuticals are removed during the wastewater treatment process. Wastewater facilities that receive industrial waste from pharmaceutical manufacturing facilities can have 10 to 10,000 times higher concentrations than those that don’t. NHS data suggests an enormous increase in prescribed antidepressants from 36 million in 2008 to 70.9 million prescriptions in 2018.  

There are 7 classes of antidepressants that use a similar mode of action: increasing neurotransmission of serotonin, norepinephrine and/or dopamine by blocking reuptake pumps. The most commonly prescribed antidepressants fall into the category of selective serotonin reuptake inhibitors (SSRI’s) including Prozac (Fluoxetine), Lexapro (Escitalopram) and Celexa (Citalopram).

The role antidepressants play in regulating hormone uptake has led some scientists to classify them as endocrine disruptors in non-target organisms. For some crustaceans, serotonin and other monoamines can play a role in color change as well as behavior: two essential functions used by juvenile shore crabs, Carcinus maenas, to escape predators. Crabs that were exposed to sub-lethal doses of antidepressants showed a lower capacity to respond to darker backgrounds as well as increased locomotion. Behavioral changes not only affect the individual but can also be detrimental at the population level and even result in trophic cascades. The wide range of roles that monoamines play in different organisms allows antidepressants to disrupt endocrine function in a variety of ways, making outcomes of contamination harder to predict. Complicating matters, organisms are rarely exposed to one type of medication let alone one type of contaminant. Combinations of pharmaceuticals as well as other contaminants can have unknown effects on behavior in a wide range of species. A combination of low doses of the antidepressant Fluoxetine and the fungicide Prochloraz were shown to alter feeding and swimming velocity in the freshwater shredder, Gammarus pulex. 

Behavioral changes in non-target species as a result of antidepressant medication exposure show the tradeoffs of using antidepressants to treat the rising rates of depression. The wide range of functions monoamines can play in different species makes it hard to predict responses to exposure and further trophic cascade effects. It is clear that pharmaceuticals will continue to play a role in shifting populations, dynamics and food sources until we are able to more efficiently remove pharmaceuticals in the environment.


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