Avoiding anxiety is one of the easiest ways to "cheat your biological clock", according to Dr Guyuron, who noted that the presence of stress was: "...one of the common denominators in those twins who appeared older". The long-standing dermatologists' nemeses of sun exposure, smoking and alcohol use were all found to have a negative effect on appearance, while the use of hormone replacement therapy (HRT) bestowed anti-ageing benefits on its users.