Genes, not lifestyle factors such as stress and diet, are most likely to cause gray hair in women, according to a study that included more than 200 identical and non-identical Danish twin sisters, ages 59 to 81.
There was little difference in gray hair among the identical twins -- who share the same genes -- and more difference among non-identical twins, whose genes differ, BBC News reported.
"This study offers us a fascinating insight into the reason why women go gray, and it certainly suggests that environmental factors are not as important as we once thought," said lead researcher Dr. David Gunn. "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 gray."
He and his colleagues also found that genes may play a strong role in receding hair, while hair thinning on top of the head is associated with lifestyle and environmental factors, BBC News reported.
The study was published in the journal PLoS One.