While antidepressants are made to improve people's mental health, the opposite reaction seems to be occurring in shrimp, which become five times more likely to commit suicide when exposed to the drug fluoxetine. 

Shrimp who show normal signs of behavior typically swim away from the light due to the fact that birds and fisherman are usually waiting to catch them in well-lit open areas. But when shrimp come in contact with fluoxetine in the water, they begin to swim toward the light putting themselves in harms way. 

Fluoxetine is released into the water by human excrement in waste water that is carried out to sea. What biologists are worried about is if enough shrimp come in contact with the antidepressant, it could cause a decline in the population, which could ultimately detriment the entire ecosystem.  

"Crustaceans are crucial to the food chain and if shrimp's natural behaviour is being changed because of antidepressant levels in the sea, this could seriously upset the natural balance of the ecosystem," said Alex Ford, a marine biologist at the UK's University of Portsmouth. "Much of what humans consume you can detect in the water in some concentrations. 

"We're a nation of coffee drinkers and there is a huge amount of caffeine found in waste water, for example. It's no surprise that what we get from the pharmacy will also be contaminating the country's waterways."

Ford began experimenting with this antidepressant problem when he found that a certain parasite could cause behavioral changes in shrimp by altering their serotonin levels. He started exposing shrimp to a small amount of fluoxetine to see if human antidepressants would affect them the same way and also wanted to know how much of this drug it would take to make them change their behavior. He found that this small amount was enough to make the shrimp harm themselves. 

"Effluent [outflowing waste water] is concentrated in river estuaries and coastal areas, which is where shrimps and other marine life live," said Ford. "This means that the shrimps are taking on the excreted drugs of whole towns."

But shellfish, like shrimp, seem to be returning the favor by exposing humans to unsafe levels of toxins as well, according to the U.S. Environmental Protection Agency (EPA).

The EPA held public hearings yesterday to review "a proposed safe exposure limit for dioxin," which is a common pollutant and waste product from smelting, chlorine bleaching, pesticides manufacturing and incineration. Adults obtain dioxin by eating shellfish, meat and dairy, and then pass it on to fetuses in the womb. According to the Environmental Working Group, adults are exposed to 1,200 times more dioxin than what they consider is safe. Furthermore, through nursing, infants consume 77 times more dioxin than what is considered safe for babies. High levels of ongoing exposure can lead to diabetes, heart disease, cancer, early menopause, reduced testosterone and endometriosis. 

Between the increase in antidepressant prescriptions in recent years and the new studies surrounding dioxin levels and their effects on humans, the exchange of toxins between people and shrimp have become hazardous to each one's health, and in some cases, fatal.