A study published by "Plastic and Reconstructive Surgery", The journal of the American Society of Plastic Surgeons and conducted on 186 pairs of identical twins has shown that environmental factors, especially what could be categorized under the umbrella heading of "stress", not just genetics, were instrumental in impacting the aging process...
Another factor linked with an older appearance has been shown to be the use of anti-depressants. They however don't say in the summary I read in French via FashionMag.fr whether that has anything to do with the medication itself or the fact that it points to the existence of a depression, or to both combined factors.
Weight-gain has also been shown to add on years to a twin when she or he is below the 40 years old threshhold, but the tendency reverses after 40 years old, the heavier twin then appearing younger. This last bit is also somewhat ambiguous a statement to me as it seems to have to do with the perception of age and our expectations of what tell-tale signs of age are, more than with an evaluation of the physical fitness of the individuals at hand, perhaps.
At any rate, you now know that if you can diminish your stress levels it will pay off in the area of facial youth!
That reminds me of an interview tidbit from Anne Hathaway who said once that her best beauty tip is to take a relaxing bath. Have you noticed how a great bath is the equivalent of applying a great beauty cream? Instant "dewrinkling"!
Think beautiful and have a great day!