The skin-brain axis has been suggested to play a role in several pathophysiological
conditions, including opioid addiction, Parkinson's disease and many others. Recent
evidence suggests that pathways regulating skin pigmentation may directly and indirectly
regulate behaviour. Conversely, CNS-driven neural and hormonal responses have been
demonstrated to regulate pigmentation, e.g., under stress. Additionally, due to the
shared neuroectodermal origins of the melanocytes and neurons in the CNS, certain
CNS diseases may be linked to pigmentation-related changes due to common regulators,
e.g., MC1R variations. Furthermore, the HPA analogue of the skin connects skin pigmentation
to the endocrine system, thereby allowing the skin to index possible hormonal abnormalities
visibly. In this review, insight is provided into skin pigment production and neuromelanin
synthesis in the brain and recent findings are summarised on how signalling pathways
in the skin, with a particular focus on pigmentation, are interconnected with the
central nervous system. Thus, this review may supply a better understanding of the
mechanism of several skin-brain associations in health and disease.
