Increasing consumption of antidepressant drugs may be helping humans but damaging the health of the bird population, according to a new study.



An expert who has looked at the effects of passive Prozac-taking on starlings says it has changed not only their feeding habits but also their interest in mating.

Dr Kathryn Arnold, an ecologist from the University of York, said: “Females who’d been on it were not interested in the male birds we introduced them to. They sat in the middle of the cage, not interested at all.”

Arnold’s research, which is investigated on BBC2’s Autumnwatch, took her to sewage works where birds flock to feed.

“They’re a really great place to watch birds because they’re attracted by all the worms and invertebrates that live there,” she told Radio Times.

“I started thinking, ‘What about what’s in the sewage?’ If you or I take a headache pill for instance, a high proportion of it ends up being excreted completely unchanged.”

She measured the level of Prozac present in earthworms living in sewage. It was tiny, around 3-5% of the average human dosage.

She then fed worms containing the same concentration of the drug to 24 captive starlings and monitored their behaviour over six months.

The birds began to display side effects similar to those reported by humans prescribed Prozac.

“The major finding was a loss of appetite. Compared with the control birds who hadn’t had any Prozac, they ate much less and snacked throughout the day. The problem then is that they’re less likely to survive long, dark winter’s nights.”

It was not just food that lost its appeal - the birds’ libido also fell.

However, in one significant area, the starlings’ reaction to the drug did not mimic its effect on the human brain - their mood remained unchanged.

Arnold said: “Antidepressants reduce anxiety in humans but we can’t ask a bird if it’s anxious; we have to measure it in a behavioural way. We present them with an unfamiliar object and see how they react. If a bird is bold, it’ll carry on feeding, even though there’s something strange in its food bowl. But we found no effect on boldness, which is what we’d expected.

“Maybe we were measuring it the wrong way and that wasn’t a particularly stressful task. If we repeated it, we’d use a different method or different novel object. Or it could be that there are enough variations between bird and human brains that Prozac works in a slightly different way.”

Autumnwatch presenter Chris Packham said there may be no simple answer. He said: “This change in behaviour could impact negatively on their ecology. We know for instance we’ve lost 50 million starlings in the UK since the 1960s.

“Pharmaceuticals could play a part. The next stage of the work is to look at wild starlings to check if they also have chemical residue in their bodies.”

Arnold said she was not attacking antidepressants or the waste-disposal industry. “I’m not saying that if you’re depressed, don’t take Prozac. Sewage treatment works are really good sources of food for birds. We’re certainly not saying they should be covered over.

“Science needs to deliver better estimates of the environmental risks posed by pharmaceuticals. The effects we’ve measured so far are quite subtle.

“These aren’t big die-offs but they could have a negative impact on wildlife. We need to find out whether they are. It’s going to get worse so we need to get a handle on it.”

Arnold recently edited a special issue of the journal the journal Philosophical Transactions of the Royal Society B on the effect of pharmaceutical contamination on wildlife.