Everybody knows that stress affects acne; acne forums are filled with stories and anecdotes, and a 2001 survey of medical school graduates showed that 67% believed stress aggravates acne. Surveys of both patients and family physicians have also raised stress as an aggravating factor in acne breakouts.

However, in spite of this, there’s hardly any research quantifying the effect that nearly everyone seems to view as common sense. A study of 22 university students attempted to quantify the effect of stress on acne severity. In the study, the researchers looked at whether there was a difference in acne severity between the end-of-term examination period and the beginning-of-term non-examination period. Results showed about 33% increase in acne during the examination period, and that acne severity closely correlated with self-reported stress levels.

Another study showed that Singaporean adolescents had more acne during examination period than during summer holiday, which the researchers attributed to increased stress levels.

Other studies have shown similar links between stress and other inflammatory skin conditions, such as psoriasis, eczema, and atopic dermatitis. Given that they all share the same inflammatory nature, it’s likely that stress has a similar effect on all inflammatory skin conditions, acne included.