Psychological

While the connection between acne and stress has been debated, scientific research indicates that "increased acne severity" is "significantly associated with increased stress levels."[18] The National Institutes of Health (USA) list stress as a factor that "can cause an acne flare."[19] A study of adolescents in Singapore "observed a statistically significant positive correlation […] between stress levels and severity of acne."[20] It is also not clear whether acne causes stress and thus perpetuates itself to some extent.