Attention on the health of university students has increased in recent years [23, 36, 37]. Acquiring and compiling knowledge about these population groups is imperative in creating health promotion activities to meet the needs and concerns of university students . Designing appropriate interventions for these groups requires insight into and an understanding of the various factors associated with students' health. The present study examined a variety of factors associated with SRHS among university students from three European countries.
In line with previous inquiries, many students in this study rated their health as excellent or very good (e.g. [19–21, 23]). From the initial five areas under investigation, only three proved to be independently associated with SRHS in students. Whereas physical, psychological aspects and socio-demographic characteristics displayed independent associations with SRHS, the area of social contacts and variables related to studying did not. Several of the variables (e.g. sufficiency of income, psychosomatic complaints, physical activity and sense of coherence) exhibited similar effects for both genders and in all three countries. In contrast, the effect of well-being was modified by gender and country, while the influence of self-efficacy was modified only by country. The effect of gender did not differ by country. We did not assess the three-way interaction between gender, country and well-being.
Some previous studies have postulated a gender difference in relation to SRHS, others have not. The observation that gender was not significantly associated with SRHS prior to considering the interactions might shed new light on these apparently contradictory findings. Although health perceptions are likely to be gender-specific (since gender is associated with many other health outcomes) , gender differences in variables associated with SRHS usually occur only for self-rated psychological health: with males rating this type of self-rated health higher . This is consistent with our findings. Such findings also lend further support to Mantzavinis et al.'s  recommendations that analyses of SRHS should consider interactions among the variables investigated.
Steptoe and Wardle  have suggested that there are culturally diverging concepts and levels of valuation of health between Eastern and Western European students, with Western European presenting more favourable ratings. In our analysis the difference as suggested by Steptoe and Wardle was only found to be true among students reporting high well-being scores while their self-efficacy was relatively low. This finding is consistent with the hypothesis investigated by Steptoe and Wardle that the cause of differences in health perception between Eastern and Western Europe might be due to a lower perception of control in Eastern European countries due to instabilities during political and economic transitions. Steptoe and Wardle's analysis was based on data collected around 1990, a time when perception of control might have systematically differed between Eastern and Western European countries. In our study, a similar average self-efficacy score was found for students from all three countries, probably a consequence of improvements of the situation in Eastern Europe since the time of economic and political transition. This could help explain the relatively small differences in self-efficacy and SRHS in the countries examined in this paper.
Psychosomatic complaints and having > 2 visits to a doctor in the last six months displayed the strongest association with SRHS in our analysis, indicating the importance of physical health in the perception of general health for university students. A previous study using open-ended questions following a self-rating of health found that adolescents and young adults more often referred to their positive health behaviours in justifying their rating than older persons who were more likely to refer to physical health problems . A qualitative study in middle-aged population indicated that health is primarily understood as absence of ill health, modified by disease specific aspects like duration, severity and consequences for everyday life . Two further studies [15, 16], using cross-sectional samples like our study, found that well-being (or psychological health) was the most important aspect for university students. While young people are less likely to suffer from chronic diseases than older people, for young people with chronic diseases still this aspect might be important for their rating of health. Also using a more common condition related to physical health like psychosomatic complaints might result in higher importance of physical health for SRHS. The prevalence of psychosomatic complaints increases steadily and considerably during the school age and complaints are highly prevalent in older school-aged children [40, 41]. Nevertheless, Piko  found that well-being explained a higher fraction of variance in SRHS than psychosomatic complaints in her sample. Her assessment is based on a forward stepwise regression model, while we evaluated partial Eta square estimates from a mutually adjusted model, which is more correct for models assessing association rather than prediction. Also, we used a different measure of well-being in our study (while the assessment of psychosomatic complaints was very similar). It is not clear whether the difference in findings can be explained by the statistical methods used or by the different well-being measure. However, the issue is further complicated by the classification of psychosomatic complaints; i.e. it is worth discussing whether such complaints truly belong to physical or to psychological health. One previous study even used a complaints score similar to the one employed in this study as a general measure of self-rated health , which further complicates the interpretation. Since gender dependency in respect to self-rated health has been postulated for psychological rather than for physical aspects , the lack of interaction between gender and psychosomatic complaints suggested the stronger connection of the latter – psychosomatic complaints- to physical health. Additionally, in our model, the effects of psychological factors were controlled for in the association between psychosomatic complaints and SRHS. Thus, the effect of the psychosomatic complaints obtained in the final model is the 'net' effect which is not mediated by any psychological factors. In addition, the WHO-5 scale applied in our analysis draws its name from the general well-being item but can also be used for the assessment of depression . Thus, by including this scale in the model, we were able to simultaneously control for the effects of different perceptions of health caused by depressive symptoms, which are frequent among university students [43–45].
This study has strengths: the relatively large sample size and the use of the same study design and questionnaire in three European countries with different socio-demographic profiles and cultural backgrounds. The analysis covered a wide range of factors, employing several variables for each of the areas under investigation; while differences in variables related to SRHS for gender and country were formally tested using interactions. Since SRHS is a useful indicator in health sciences, this inquiry has contributed to a reversal of two trends in the published literature: studies either employing too few variables, ultimately resulting in a constricted view and scope of self-rated perceptions of health, or alternatively, focusing predominantly on elderly populations. Hence, this study has bridged these gaps and contributed to the literature focusing on a young adult population and analysing a broad range of factors associated with SRHS. Both of these critical aspects have been highlighted in literature as being insufficiently considered [16, 24].
The study has also some limitations. Findings are based on self-reported data with no validation undertaken. SRHS is genuinely a subjective measure of one's health, but the number of visits to a doctor could have been externally validated. Furthermore, cross-sectional approaches allow conclusions about associations, not causations. It could be that observed associations are reinforced by reversed causality, whereby not only a given behaviour or condition leads to a decreased SRHS, but also a decreased SRHS influences the behaviour/condition. Since this inquiry examined only one university per country, differences between countries could be in fact differences between universities. The questionnaire did not contain a direct question assessing the presence of severe, acute, or chronic illness. Instead, we used the number of visits to a medical doctor as a proxy for having such illnesses (> 2 visits in last 6 months). This could have had two effects: first, some students could have consulted a doctor more often without having a severe, acute, or chronic illness; conversely, some of chronically ill patients may not see a doctor as frequently (e.g. when on stable medication). Also, some students may have repeatedly visited a doctor because of mental health conditions. However, despite some potential misclassification, students experiencing illness are more likely to be found in the group visiting doctors more frequently and vice versa. For the statistical analysis we used the framework of a general linear model despite the outcome variable having only five discrete values, implicitly assuming that the differences between subsequent values of the scale were equal and that the normal residual error was well approximated.