Bold, hungry, anti-social, but anxiety-free fish

By: Dana Sackett
We have all seen the numerous drug advertisements on TV with their list of ridiculous disclaimers and adverse effects. These commercials are an indication, and have even been considered the reason behind, the increased societal use of pharmaceuticals drugs in recent years. In fact, it was only in 1997 that the FDA allowed drug companies to start promoting their products on television. However, trouble occurs when those chemicals pass through our body and through wastewater treatments plants, which are not equipped to remove them from wastewater, and enter our local aquatic environments.



Most pharmaceuticals used to treat anxiety contain a class of psychotherapeutic drugs called benzodiazepines (e.g. valium, xanax, klonopin, ativan, oxazepam). These drugs can pass through wastewater treatment plants and are resistant to degradation, meaning that they can persist and concentrate in rivers and streams. Problems arise because benzodiazepines are designed to alter behavior through a pathway common in a wide range of animals; a pathway that causes neurons to be less excitable and slow signal transmission throughout the brain.

Effluent discharge is a form of point pollution. Credit: Ronald Toms. Source:

A recent study from Sweden found that oxazepam, an anti-anxiety drug, has been shown to alter the behavior of wild European perch at concentrations commonly found in the environment. Fish exposed to the drug became bolder (measured by the time it took to enter a novel or unknown area), more active, had a lower prevalence of shoaling, and ate more food at a faster rate causing them to deplete there resources quickly.

GABA A receptors on the end of a post-synaptic neuron. Benzodiazepines binds to the GABA receptor, which causes a structural change in the receptor that results in an increase in channel openings. This allows more chloride ions to move through the channel into the neuron and lowers the action potential of the neuron.   Source:

Bold, hungry, anti-social fish might sound funny, but on an ecosystem level it can be very problematic. Fish behavior is crucial to their ecological fitness. For example, behavior drives foraging, predator avoidance, reproduction and survival. Altering fish behavior could, therefore, have serious affects on numerous other species and eventually how the entire ecosystem functions.

In this instance, an increased feeding rate could result in cascading affects on primary production (algae) because fish are consuming a large portion of primary consumers (zooplankton), while increased boldness and activity, with a lower prevalence of shoaling could easily increase predation risk, causing population declines. The authors of this study conclude that waters contaminated with just this single anti-anxiety drug, oxazepam, are likely to affect fish ecological fitness and food-web structure.
European perch swim in waters laced with the anti-anxiety drug oxazepam. Credit: Bent Christensen; USDEA. Source: 

More concerning, is that in the natural environment there are often more than just one chemical or type of anti-anxiety drug in the water, and additive effects have been seen when different types of benzodiazepines are mixed together. Also, with the recent increased use of these drugs and the projected continued increase as they become more available for the growing global population, we may be on the cusp of what is to become a big problem.

A satire advertisement making fun of pharmaceutical industry marketing in the United States. Source:

Next time you see one of those drug commercials, don’t just fast forward through it, watch it, it may have a new disclaimer that states, “may also cause ecological havoc in local ecosystems.” After all the FDA states that, “all advertisements promoting medical use of prescription drugs …must include a ‘major statement’ prominently disclosing all of the major risks associated with the drug.”  It appears major risks may extend beyond just the person with the prescription.


References and Resources:

Brodin T., Fick J., Jonsson M., Klaminder J. 2013. Dilute concentrations of a psychiatric drug alter behavior of fish from natural populations. Science 339:814-815.

Johansson F, Brodin T. 2003. Effects of fish predators and abiotic factors on dragonfly community structure. Journal of Freshwater Ecology 18:415

Smith BR, Blumstein DT. 2008. Fitness consequences of personality: a meta-analysis. Behavioral Ecology 19:448.

The World Medicines Situation (World Health Organization, Geneva, ed. 3, 2011).

Please leave a thought provoking reply. We reserve the right to remove comments deemed inappropriate.

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.