They help humans to be happy - but for shrimps, anti-depressants are proving to be fatal.
A study by the University of Portsmouth reveals the anti-depressant - fluoxetine - is having a damaging affect on the creatures as it causes them to swim to the light, making them vulnerable to birds and fish.
Experts say the drug, which combats depression, is being used by more people and is passed through the sewer system into coastal waters, like the Solent.
The drug increases serotonin levels which makes humans happy, but for shrimps it draws them towards the light of the water's surface.
Dr Alex Ford, from the University of Portsmouth's Institute of Marine Sciences, says because shrimps are at the bottom of the food chain, this could have a damaging affect on all sea life.
Speaking to The News, he said: 'For some time scientists have known that prescription chemicals are getting into the water. I wondered if the drugs which are used to treat depression might also change the behaviour of shrimps.
'They are at the bottom of the food chain so this could seriously upset the natural balance of the ecosystem.
'There are millions of shrimps in the Solent and they are taking in excreted drugs of whole towns.'
Dr Ford conducted the simple experiment by putting shrimps into a tank of water and filled it with the same concentrated level of fluoxetine found in coastal waters.
And he found that they were five times more likely to swim to the light than shrimps who hadn't been exposed to the drug.
He added: 'Usually shrimps swim to darkness, like under rocks, it is a survival technique.
'When the shrimp swims out into the open they get gobbled up.
'People don't always realise that the drugs that they take don't get broken down very well through the sewer system.'
The research has now been published in the journal Aquatic Toxicology.
Prescriptions for antidepressants have risen rapidly in recent years, yet the environmental effect of pharmaceuticals in sewage has been largely unexplored.
Dr Ford now hopes to look at the affect of other pharmaceutical drugs on sea life.
'It is quite a new topic and there are so many drugs on the market,' he added.
>> Vote in our latest web poll.