Kaess et al. BMC Public Health 2011, 11:597 http://www.biomedcentral.com/1471-2458/11/597 cross-sectional design relying on self-report question- naires might be that higher reported prevalence rates of suicidal behaviour in girls could also have occurred due to self-report bias influenced by their current mood stages. However, this bias mainly occurs during self- report assessments of adverse childhood experiences or life events which usually try to assess quite subjective appraisal. In contrast, our questions on suicidal thoughts and particularly suicidal acts seem to be more distinct and therefore less prone to self-report bias. The strength of this cross-sectional design is its anon- ymity, which heightened the acceptance of all involved parties and was a prerequisite on the part of the school authorities. Several factors strengthen the validity of the findings reported in this study. First, our sample was representative of ninth-grade students in Germany as we had a large sample and a low dropout rate. Secondly, we used a clear definition of suicidal behaviour, divided into suicidal ideation and suicide attempts. Thirdly, ado- lescents’ reports may be of enhanced validity as this sur- vey was based on a self-rating conducted anonymously. Conclusions From the results of our study we could draw the follow- ing main conclusions: First, there are remarkable gender differences in both, adolescent non-fatal suicidal behaviour and emotional and behavioural problems. Females are more likely to be engaged in non-fatal suicidal behaviour and to suffer from emotional and behavioural problems during adolescence. Second, different occurrences and extents of emo- tional and behavioural problems in females and males might explain the gender differences in suicidal beha- viour to a large extent. These findings may support the differential psychopathology theory, which explains gen- der differences in terms of occurrence of suicidal thoughts and non-fatal suicide attempts by different rates of psychopathology with females suffering more from internalizing disorders [13,20,43]. Our results indicate that female adolescents are at specific risk of experiencing non-fatal suicidal beha- viour. They emphasize the importance of non-fatal sui- cidal behaviour during adolescence as an issue of public health and clearly distinguish the need to con- sider female and male adolescents separately concern- ing their risk for suicidal behaviour and, particularly, the leading psychopathological characteristics of suici- dal behaviour. Additionally, the findings clearly show that the higher rate of psychopathology in female ado- lescents is strongly associated with suicidal behaviour and therefore may possibly represent a main aetiologi- cal factor as compared to males. Therefore, either detection or prevention and treatment of suicidal Page 6 of 7 behaviour in adolescents should especially focus on the gender differences in emotional and behavioural pro- blems during adolescence. Acknowledgements We thank all students in the region of Heidelberg for participating in the study and the school staff of the participating schools for helping perform the study. Many thanks to all co-workers from the Department of Child and Adolescent Psychiatry that helped to perform the study. The study was mainly funded by the faculty of medicine at the University of Heidelberg and the Public Health Department of Heidelberg. There was additional funding by the Lautenschläger-Foundation, wherefore we would like to give many thanks to the Foundation for the support of our research. Author details 1Department of Child and Adolescent Psychiatry, Centre of Psychosocial Medicine, University of Heidelberg, Heidelberg, Germany. 2Public Health Department of Heidelberg, Heidelberg, Germany. 3Department of Educational Psychology, University of Education Heidelberg, Heidelberg, Germany. 4Orygen Youth Health Research Centre, The University of Melbourne, Melbourne, Australia. Authors’ contributions MK designed the analysis plan, analysed the data, interpreted the findings and wrote the first draft of this paper. PP and RB helped develop the analysis plan, analysed the data, and helped interpret the findings. JH had the idea of the study. MK, PP, RS, JR, MK, RB and FR helped design and implement the study. MK and FR obtained funding. All authors contributed to the writing of this paper and read and approved the final manuscript. MK is the guarantor. Competing interests The authors declare that they have no competing interests. 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