Having an orgasm that lasts for three hours might sound like fun to many but for Liz, from Seattle, the experience was anything but.

Instead, she says it was fun 'for the first five minutes' but soon descended into a nightmarish experience that left her needing hospital treatment.

Worse, the marathon orgasm proved to be the first of a series of unwanted sexual spasms that could strike anywhere and at any time.

'Initially it was just after sex but eventually, it got to the point where I could be doing anything from watching TV, walking down the street and I would have an orgasm out of the blue,' explains Liz.

When the orgasm failed to stop, Liz, panicking, began ringing every doctor she'd ever been to in the hopes of finding a way of stopping the unwanted sensation.

With the help of boyfriend Eric, she tried hopping on the spot, drinking a glass of wine and even took antihistamines in an effort to stop it.

Realising that it wasn't about to stop, Eric insisted on taking Liz to A&E where doctors were left baffled by the continuing orgasm.

'Having to walk while having an orgasm is like walking in jello,' adds Liz. 'It's a difficult thing to do. I remember having to put mind over matter to make it work.

'The doctors kept asking me, "Are you sure your partner didn't drug you or something like that?" And I was thinking, "Why on Earth would Eric drug me?",' she adds.

Eventually, the orgasm stopped - without the help of medics who had been unable to establish the cause.

'At first, it was just sheer disbelief,' adds Liz of the moment the orgasm finally ended. 'I thought it was going to start right back up but it didn't.

'It's a physically, emotionally and mentally taxing experience to have an orgasm for three hours.'

But although the marathon orgasm had ended, her problems hadn't as she endured near-continuous orgasms, sometimes having as many as 12 a day.

Doctors, initially baffled, eventually pinpointed the cause of the problem - bipolar disorder which had been misdiagnosed as depression and treated with anti-depressants.

'Anti-depressants exacerbate multi-orgasmic dysfunction because they actually change brain chemistry, that's their job,' comments Dr Irwin Goldstein, director of the Institute of Sexual Medicine in the USA.

To tackle both the bipolar disorder and persistent orgasms, Liz was given valproic acid - a substance that treats bipolar while at the same time suppressing the brain chemicals used during orgasm.

'I got down from where I was to having them only daily, then to one every other day, then I was having them weekly and then maybe it was about once a month,' says Liz.

'It took about four to five months before they were completely under control and it's probably been about a year since I've had one.

She adds: 'My diagnosis is that I probably have to take meds every day for the rest of my life and I don't live in fear. I have a very happy sex life and I don't have to live in fear.'