Instead of failing to get aroused, women suffering from persistent sexual arousal syndrome (PSAS) experience constant, unprovoked feelings of excitement.

"Persistent sexual arousal syndrome occurs when a woman becomes involuntarily aroused for extended periods of time in the absence of sexual desire," said Dr David Goldmeier, of St Mary’s Hospital in London.

But rather than being a pleasant sensation, Goldmeier, who described PSAS in a report in the International Journal of STD & AIDS, said it is embarrassing and very distressing for women.

Some sufferers have reported being suicidal, he added.

In the majority of cases the cause is unknown but a number of women report symptoms after they stop taking antidepressants known as selective serotonin reuptake inhibitors.

Because so few cases have been studied, little is known about the prevalence of the problem or the best treatments for a condition that was first diagnosed in 2001.

"It deserves continued research, not only because it is a distressing and perplexing condition, but also because … treatment may lead to greater understanding of other aspects of female sexual response," said Goldmeier and Dr Sandra Leiblum of the Robert Wood Johnson Medical School in Piscataway, New Jersey.

The International Journal of STD & AIDS is published by the Royal Society of Medicine in London.