BMC Public Health 2009, 9:340 http://www.biomedcentral.com/1471-2458/9/340 1,9 1,8 1,7 1,6 1,5 1,4 1,3 1,2 1,1 1 No A little Quite a lot Very much Acne FCMihegeauncrkescL1oisrte)s on HSCL-10 (The 10 item Hopkins Symptoms Mean scores on HSCL-10 (The 10 item Hopkins Symptoms Check List) with increasing severity of self-reported acne (no, a little, quite a lot and very much) in late adolescence among both genders in Oslo, Norway. mental health was identified [21]. Acne was objectively assessed by the Global Acne Grading System and mental health by the Hospital Anxiety and Depression scale in the Turkish study. The reason for these conflicting results is not obvious, but since there are many different instruments used to carry out the measurements and low number of participants in some of the studies, it is hard to compare the results. How- ever, there are other observations that point to a link between mental health problems and acne. First of all, acne is a visual condition and may therefore cause a vari- ety of psychosocial effects such as decreased self-confi- dence, social impairment, depression and anger [39]. Second, it is possible that mental health problems cause or increase acne. This is probably not as obvious, but there are several points that may support this view. Stressful events can exacerbate acne, as shown in a sample of 22 university students [40]. The prevalence of mental distress is very high in late adolescence when acne is very com- mon. From Oslo the prevalence of mental distress among 15-16 year old adolescents are 18%, in the present study (18-19 year old adolescents) 26% and among adults 13% [41,42]. It is suggested that neurogenic factors could con- tribute to the onset or exacerbation of acne formation, possibly via the neuropeptid substance P and increased number of nerve fibres around the sebaceous glands in acne patients [43]. Stress can elicit substance P from peripheral nerves and thereafter may accelerate lipogene- sis in the sebaceous glands [43]. The increase in nerve fibres in acne-prone skin may result from raised expres- sion of nerve growth factor on the sebaceous glands which act as a neurotrophic molecule stimulating the sprouting of nerve fibres in the skin [43]. In addition receptors for corticotrophin-releasing hormones have been identified on human sebocytes, especially acne-involved skin [44,45]. Corticotrophin-releasing hormone can be one neuroendocrine factor that contributes the development and exacerbation of acne [44]. It has also been reported that antidepressive medication can improve acne [46]. Finally, there may be one or more common factors influ- encing both acne and mental problems. Medication can be one such factor, and the widely used drug for acne, isotretionoin, has been linked to an increase in depres- sion, but no causal relationship has been established [47,48]. Unfortunately neither in the present study nor in other studies exploring the association between acne and mental problems [15-17,21,22] is isotretinoin introduced as a possible confounding factor. However, information from the Norwegian Prescription Database shows that 27 individuals living in Oslo, 5 girls and 22 boys, born in 1986 were dispensed isotretinoin at a pharmacy in 2004. It is not very likely that such a low number of users could explain the main finding in this study. Finally, another variable that could influence both acne and mental health is diet [30]. In the present study an association between acne and a low intake of raw vegetables and a high intake of choco- late/sweets and potato chips has been found, but in the adjusted model the association with raw vegetables remains significant only among girls. This has never been shown before. Recently there has been renewed interest in the link between acne and diet. A small randomized con- trolled study has shown that a low glycaemic diet decreases the number of acne lesions after 12 weeks [23]. Interestingly the protective effect of a high intake of vege- tables and low intake of chocolate/sweets and potato chips in the present study is in coherence with the hypoth- esis that a low-glycemic diet is beneficial to arrest the development of acne. However, we did not find that high intake of fish had a protective role in the development of acne, contrary to what has been suggested [30,31]. Longi- tudinal observations have discovered that a high intake of milk is associated with acne [13,14]. Unfortunately we did not have data on the intake of milk in this study, and the- oretically milk could have been a confounder in the explo- ration of the association between acne and mental distress. However, milk is probably not a confounder, since there is no established evidence for an association between consuming milk and mental problems. We have Page 6 of 8 (page number not for citation purposes)