A woman's genes¹ are much more likely than lifestyle factors such as stress or diet to cause greying hair, a study suggests.

研究显示，一个女人的基因比诸如压力、饮食之类的生活方式因素更容易引起白头发。

There was very little difference in the greying of identical twins

Unilever（联合利华） scientists studied more than 200 identical（相同的，同一的） and non-identical Danish twin sisters aged² between 59 and 81.

The scientists found little difference between the greyness of the identical twins（同卵双胞胎） - who share the same genes.

But there was more difference between non-identical twins, whose genes differ, the study found.

The study, published in the journal PLoS One, also suggests receding³ hair is linked to mainly genetic⁴ factors（遗传因子）.

But it indicates hair-thinning on the top of the head is connected to environmental and lifestyle factors.

On the issue of greying hair, lead researcher Dr David Gunn said although many theories had been put forward to explain different rates of greying, there was little hard scientific evidence to back them up.
 
He said: "This study offers us a fascinating（迷人的） insight into the reason why women go grey and it certainly suggests that environmental factors are not as important as we once thought.

"The research indicates that irrespective of how stressful a woman's life is, there are greater forces at play which are more likely to cause her hair to grey."

Nina Goad⁵, of the British Association of Dermatologists⁶, said previous work had also found few identifiable environmental factors among people who went grey much earlier than their relatives.

"This means that for the majority of people, greying hair is not down to（一直到） something you have done, but to genetic factors beyond your control, and that generally your lifestyle will not greatly impact on when your hair loses its colour," she said.

"There are of course exceptions to this rule."