The impact of perceived stress on skin ageing.

Skin ageing can be divided according to phenotypical features into intrinsic (by the passage of time) and extrinsic (with the addition of the effects of environmental factors). Photoageing is by far the most researched factor of extrinsic ageing but the additional impact of other factors such as cigarette smoking and exposure to air pollution ought to be taken into account. One of the least researched topics in relation to extrinsic skin ageing is the impact of psychological stress. A contemporary review of response of human skin to stress describes the molecular mechanisms of extrinsic skin ageing, but has fallen short of explaining resilience to stress exhibited by people. Mechanisms to regulate gene expression, define cellular identity and promote functionality are responsible for the adaptive response to stressful events. Conversely, maladaptive response of human tissues to chronic stress appears to have an impact on gene regulation. Epigenetics is the study of heritable changes in organisms due to modifications in gene activity and expression, as opposed to the genetic code (DNA genome). Chronic stress appears to be an important factor in determining an individual's vulnerability to ageing and age-related comorbidities via epigenetic modifications. Forerunners in epigenetic research recognized the necessity of a reliable biomarker in order to develop a better understanding of the role of epigenomics in ageing. Genomic DNA methylation patterns (DNAm) appear to be valuable in age prediction but variability in specificity exists across species of mammals, human races and tissues. Neuroscience research appears to be leading the way in epigenomics whilst the lack of a valid and reliable DNAm-associated age predictor compatible with human skin tissue hinders research endeavours for the epigenetics of skin ageing.