On the evening of 15 February 1996, the 147,000 tonne tanker Sea Empress ran aground on rocks at the entrance to Milford Haven harbour in south-west Wales. (The ship’s pilot, it later emerged, had been making his first ever solo attempt at the manoeuvre.) Over the next week, 72,000 tonnes of crude oil and 360 tonnes of heavy fuel oil seeped from the wreck into the sea, contaminating 200 kilometres of the Welsh coastline, much of it part of the exceptionally beautiful and ecologically diverse Pembrokeshire Coast National Park. More than 50,000 birds were killed or injured. The devastating effects of the Sea Empress disaster weren’t confined, however, to the flora and fauna of the National Park. In the wake of the oil spill, local people found themselves experiencing a range of health problems, including headaches, nausea, and skin irritation. And yet when we look closely at these accounts, something curious emerges. The first symptoms were reported as early as the first day of the incident. But at that stage very little oil had escaped from the wrecked tanker. Whatever was causing these first headaches and feelings of nausea, it wasn’t the Sea Empress. Indeed, people living on stretches of the coast that were entirely unaffected by the spill also complained of symptoms. How do we explain physical symptoms without an obvious physical cause? In the case of the Sea Empress disaster, it’s likely that they were the direct result of anxiety. It’s an established formula. Take one catastrophe, add extensive media coverage, and watch public anxiety grow. Think back, for example, to the anthrax scares that swept the US in September and October 2001. During these weeks, letters containing anthrax spores were sent to a number of senators and media organizations. Five people died and a further seventeen were also infected. (To date, the case is still unsolved.) With anxiety in the US already ratcheted to unprecedented levels by the September 11 attacks, hundreds of people soon began reporting that they too had been the victims of anthrax poisoning, with many complaining of symptoms.