Kaess et al. BMC Public Health 2011, 11:597 http://www.biomedcentral.com/1471-2458/11/597 disorders while males tend to suffer from externalizing emotional and behavioural problems [18-20,33]. Given these differences in internalizing and externalizing psy- chopathology, it could be hypothesized that boys tend to act out their personal problems and therefore are more likely to show aggressive (externalizing) behaviours while girls more often show auto-aggressive (internaliz- ing) symptomatology. An important finding of our study is that the gender effect is more distinct for internalizing emotional and behavioural problems with far higher rates of internaliz- ing problems in female students and males presenting only a marginally higher rate of externalizing problems. Female adolescents did not only show considerably higher values for somatic complaints, depression and anxiety but also suffered from more emotional and behavioural problems on the whole. A possible explana- tion for the fact that female adolescents suffer from more emotional and behavioural problems than same- aged males could be the significant margin of adolescent development in females during this period. It is well known that psychopathology is rare during childhood and increases during adolescence [34]; thus, females aged between 14 and 16 are usually further along in their development and therefore might present with more emotional and behavioural problems than do males. Suicidal behaviour might then increase later in male adolescents’ lives which already could be demon- strated in previous research [35]. As delinquency is also highly associated with suicidal behaviour, it could be hypothesized that this consequently might be the more male pathway into suicidal behaviour. Additionally, some authors have argued that females are more likely to communicate their problems to others and to engage in help-seeking behaviours but at the same time they are also more likely to ruminate about problems they encounter which can affect their wellbeing, and conse- quently might be a cause for gender differences espe- cially in internalizing problems [2]. Another possible explanation for differences in both emotional problems and suicidal behaviour might be different experiences of childhood adversities, as e.g. childhood sexual abuse is much more common in girls and is also strongly related to depression, self-harm and suicidal behaviour during adolescence and adulthood [36]. A more neurobiological approach to explain gender differences in psychopathol- ogy has previously been reported by Schneider and col- leagues who found differences in emotion processing that might account for such gender differences [37]. Our findings suggest that there is an exceptionally strong association for depression, anxiety and delinquent behaviour with suicidal behaviour. This is consistent with findings from many other studies that reported emotional and behavioural problems to be strongly Page 5 of 7 associated with suicidal behaviour and gave evidence for a correlation of suicidal thoughts and suicide attempts with both internalizing and externalizing problems [20,38-42]. The main purpose of this study was to investigate potential gender differences in emotional and beha- vioural problems and the extent to which these are pre- dictive of adolescent non-fatal suicidal behaviour. Our results clearly demonstrate that gender alone does only explain 2.3 -2.7% of the information of non-fatal suicidal behaviour, while emotional and behavioural problems explain 23.2 -30% of the information. By adding gender to the emotional and behavioural problems only an additional 0.3% of information can be explained, which, however, is still significant due to the large sample size, but practically hardly relevant. This finding may strongly support the hypothesis that explanations for gender dif- ferences in rates of suicidal behaviour may arise from gender related differences in psychopathology [12], as it is in line with findings of Fergusson and colleagues who also supported this theory [19]. However, it has to be acknowledged that, regarding the whole model of suici- dal behaviour, there are many additional influencing fac- tors which could not be included in this analysis. Nevertheless, adolescent psychopathology seems to be responsible for the by far largest portion of gender differences. Overall, the results of our study support the view that girls clearly are at higher risk of engaging in non-fatal suicidal behaviour during adolescence. Notably, emo- tional and behavioural problems during this period in life could play an important role in this regard. In con- clusion, girls may be more likely to exhibit suicidal behaviour because they suffer from a higher rate of emotional and behavioural problems during adolescence. This finding could to a large extend explain the existing gender differences in suicidal behaviour and should be considered as one main reason for these gender differ- ences [13,19,43]. However, we still need to understand the missing link between gender and adolescent psycho- pathology which could range from genetic and neuro- biological aspects to adverse childhood experiences and other environmental factors. The overall interpretation of our findings is limited by the cross-sectional design of the study. Therefore it is not possible to determine whether the elevated rates of emotional and behavioural problems are the cause rather than the consequence of suicidal behaviour. A possible causal relationship can only be investigated in a longitudinally designed study. However, the fact that the investigation took place at the onset of suicidal beha- viour – as there is evidence that suicidal behaviour begins in early to middle adolescence – could at least alleviate this limitation. One additional problem of this