Can people be addicted to the sun? Perhaps, at least they may get an opiate effect from it. 

A study found that UV exposure leads to elevated blood levels of β-endorphin in mice and causes systemic analgesia - mice who had a lot of UV exposure were less sensitive to touch and temperature and walked with erect tails. Signs that the endorphins were producing opioidlike effects.

The researchers then injected the mice with a drug that blocks opioid receptors and found that after a dose of the drug, sensitivity and tails immediately went back to normal. They even underwent withdrawal symptoms.



Read more: Is the sun getting you high? by Nadia Whitehead, Science

Citation: Gillian L. Fell, Kathleen C. Robinson, Jianren Mao, Clifford J. Woolf, David E. Fisher, 'Skin β-Endorphin Mediates Addiction to UV Light', Cell Volume 157, Issue 7, p1527–1534, 19 June 2014 DOI: http://dx.doi.org/10.1016/j.cell.2014.04.032