Effects of Antidepressants on Fish, by Tal Tomlinson

Many people throughout the United States deal with personal issues like depression on a daily basis. Awareness and the scientific study of mental illnesses has risen within the past decade. Luckily, there are doctors who can talk patients through their struggles and, if necessary, prescribe them antidepressant medication to make their lives as peaceful as possible. Prescribed medications contain different chemicals that affect the nervous system in many ways. However, medications such as antidepressants have uncertain effects in the aquatic environment. For example, the chemical ingredients released from prescribed medications can have negative effects on fish behavior and their neuro systems.

Fish as a species have been studied for hundreds of years dating back to the incorporation of fish in Aristotle’s scientific studies in 330 AD (Aristotle & Balme 1991). Their anatomy, physiology, and ecology have been consistently studied by environmentalists since the evolution of technology. However, due to the recent improvements and the introduction of substances like antidepressants, scientists have only begun studying their neurological effects on fish due to a fluctuation in observed behaviors. Fish are known to have a fairly simple brain, but they can still process semi-complex situations like interacting and avoiding predators. At this time, scientists are trying to figure out why these interactions and relations have decreased.

Fathead Minnow were prey species in study of predator avoidance by Painter et al. 2009.  Photo by Ted Fauceglia.

Antidepressants (citalopram, paroxetine, sertraline, venlafaxine, and bupropion, and their metabolites norfluoxetine and norsertraline) were detected in gonad, brain, muscle, and liver organs of Largemouth Bass and other fishes from Niagara River (Arnnok et al. 2017).   Photo by Neil DeMaster. CC BY-ND- 2.0

In one study by investigators from the Université de Montréal, it was found when bodies of water are contaminated and fish are exposed to anti-depressants, they begin to exhibit a reduction in prey avoidance behavior in Fathead Minnow Pimephales promelas. This is due to the inhibition of specific neurotransmitters, such as “…serotonin (5‐hydroxytryptamine; 5‐HT), norepinephrine (NE), and dopamine (DA)” which are blocked or altered by the contaminant (Painter et al., 2009).  All of these chemical hormones are crucial to both the central and peripheral nervous system of the fish. If there are even slight changes in the neurological concentration of the body from outside sources, it could affect many different intrinsic systems. One of which is the behavior of complacency toward predator threats. Antidepressants and prescribed medications cause a panic in the fisheries science community because many of the ingredients that make up the drugs are serotonin inhibitors. Serotonin, a neuro hormone found in both human and fish brain tissue, is used to regulate emotion, sleep cycles, and even the “fight or flight” response when posed to threats. When antidepressants are introduced into an ecosystem at a human specific concentration, between 5-40 mg depending on body size (Phelps 2015), it can completely destroy the neurotransmitters that the chemicals adhere to due to overload. This in turn causes the behavioral complacency.

Venlafaxine affected predator avoidance behaviors of Fathead Minnow (Bisesi et al. 2014).

Complacency is an issue due to the fact that fish who reside in a watershed where antidepressants have been introduced may also interact with fish from other areas who have not. Once in this environment where all other fish have normal behavior, the changes become apparent. Fish species who have not been altered by the effects of antidepressants are able to attack and prey upon the newly affected fish. Due to the destruction of the chemoreceptors in the brain, they begin to lack fear and swim towards predators. However, these affects also work in the opposite direction. Fish species who have been affected by the ingredients of antidepressants have a significantly decreased ability to catch prey and feed.  Bisesi et al. (2014) found that bass who were exposed to venlafaxine, a commonly prescribed antidepressant, showed increased prey capture time in all 6 of their studies. They were beginning to capture prey at a much slower rate than if they had not been affected. Another effect they found to be true was that with the introduction of venlafaxine, there was a statistically significant reduction in the serotonin found in brain tissues of fish (Bisesi et al. 2014). Its exposure to the watersheds has become detrimental to fish neurosystems and behavior. Despite their hypothesis being proven, they are left with mostly open-ended data. In their conclusive statement they confer, “Brain serotonin alone did not adequately explain behavioral results. Serotonin response in other tissues as well as peripheral effects may have accounted for additional behavioral responses after brain serotonin reached a depressed steady state.” (Bisesi et al. 2014), thereby explaining that more studies must be conducted in the same manner to have conclusive and evidential proof.

Understanding the behavior of the fish and how these chemicals affect them is extremely important. However, it is also very important for us to understand how these chemicals are getting into the environment. If no solution is found to address this issue, there could be serious declines in fish populations in the future due to the change in behavior observed in fish that have been exposed to antidepressants. The chemicals making up these substances are causing fish to become complacent and not willing to feed or mate. These are serious issues which need to be addressed in order for fish to live normally. Eliminating these adverse side effects are critical in order to maintain healthy ecosystems, maintain species diversity and preserve the sport of fishing. Improved processes  more effectively removing these medications and their metabolites from wastewater are needed to prevent the loss of biological diversity in our lakes and rivers (Arnnok et al. 2017).

References

Aristotle, and D. M. Balme. 1991. History of animals. Harvard University Press, Cambridge, MA.

Arnnok, P., R.R. Singh, R. Burakham, A. Pérez-Fuentetaja, and D.S. Aga.  2017. Selective uptake and bioaccumulation of antidepressants in fish from effluent-impacted Niagara River.   Environmental Science and Technology 51:10652-10662.  

Painter, M. M., M. A. Buerkley, M. L. Julius, A. M. Vajda, D. O. Norris, L. B. Barber, E. T. Furlong, M. M. Schultz, and H. L. Schoenfuss. 2009. Antidepressants at environmentally relevant concentrations affect predator avoidance behavior of larval Fathead Minnows (Pimephales promelas). Environmental Toxicology and Chemistry 28(12):2677.

Phelps, J. 2015. What Is an Adequate Dose of an Antidepressant?” Psychiatric Times, October 5.  Accessed on 30 April at www.psychiatrictimes.com/depression/what-adequate-dose-antidepressant

Bisesi, J.H., Jr., W. Bridges, and S.J. Klaine. 2014. Effects of the Antidepressant Venlafaxine on fish brain serotonin and predation behavior.  Aquatic Toxicology 151:88-96. doi: 10.1016/j.aquatox.2014.02.015.