Based on data of the 2012 Swiss Health Survey, the present analyses revealed positive associations between BWD and depression independent of sex, age and BMI. To our knowledge, this is the first time these associations are studied in Switzerland.
Depression is the most common psychiatric disease in Switzerland. In the present study, 6 % were affected by a major depressive disorder according to the PHQ-9. Our estimate is in line with the estimated prevalence of 6.9 % in the European Union .
BWD has impact on nearly one fourth of the population living in Switzerland. The highest peaks were observed in middle-aged, 35–60 year olds. This proportion is a lot lower than the one found in a cross-sectional population-based German study , in which body weight dissatisfaction was reported by 40 % of the 25–74 year old men and women. However, body weight dissatisfaction was not assessed in the same way as in the SHS, which may have resulted in the observed difference.
The observed association between BWD and depression in the present study is in accordance with findings from surveys conducted mainly in adolescents and looking at the associations of various components of body image with depression [2, 19, 26–29]. In a U.S. study  on 2,139 adolescent males who were followed into adulthood, boys who had an average weight and perceived themselves as overweight or very underweight stated significantly more depressive symptoms than boys without body weight distortions. This result did not change over the 13-year follow-up period. In another longitudinal study among US adolescents body dissatisfaction was a predictor of depression for females but not for males . In a cross-sectional study among Portuguese adolescents  on the other hand, body dissatisfaction contributed to depressive symptoms, without gender differences.
But in general women tend to internalize a thin appearance ideal , whereas the ideal male body is one of lean muscularity [2, 31]. Thus, our question on body weight satisfaction may not be precise enough to distinguish between obesity and muscularity. Since both obesity and muscularity dissatisfaction are of importance of the masculine body image upcoming research should assess both of them . Although sex did not modulate the associations between BWD and depression, women tended to be more often dissatisfied than men.
In adults, the evidence is limited and not yet conclusive [5, 8, 16, 17, 32]. A cross-sectional analysis of the American Study of Women’s Health Across the Nation (SWAN)  observed that middle-aged women with body image dissatisfaction or who perceived themselves as “unattractive”, but not those with BWD, were more likely to report clinically significant levels of depressive symptoms. Also in a study conducted with 97 mainly female U.S. patients with binge eating disorders, body image disturbance was positively associated with depression . In contrast, a prospective survey among Spanish university graduates, showed no association between body image disturbance and subsequent depression neither in adult men nor in adult women .
Others investigated whether body weight categories may modulate the association between BWD and depression. A variety of studies conducted with children or adolescents observed that perception of body weight may be more important than objectively measured weight in the relationship with mental health, e.g. with suicide ideation or attempts [33–36]. Furthermore, in a cross-sectional Chinese Study  adolescents who perceived themselves as overweight were more likely to experience depressive symptoms than those who perceived themselves as normal and/or underweight. In the same study, no significant association between depressive symptoms and actual measured weight status was observed. In a population-based cross-sectional American Study (NHANES) with over 13,000 participants, women who perceived themselves as underweight or overweight had an increased odd of depression compared with women who perceived themselves as about the right weight. This association was independent from measured weight. Among men, perceiving oneself as underweight but not being underweight (objectively measured) was associated with depression . Accordingly, in our study, BWD remained to be associated with depression after adjustment for BMI. Thus, we confirmed the results of previous studies showing that perception of body weight might be a better predictor for depression than actual weight status.
Moreover, in our study, BWD was not only positively associated with depression in underweight, overweight and obese individuals but also in those with normal weight. Similarly, a recent cross-sectional study on Chinese adolescents looked at the moderating factors between the association of body dissatisfaction and depression. They observed significant associations in underweight, normal weight and overweight females, but in males associations were only observed in underweight and normal weight adolescents .
Potential mechanisms how body dissatisfaction is associated with mental health have been postulated previously [11, 19], focusing on the fact that body dissatisfaction stems from an inappropriate emphasis on the importance of thinness and other unachievable standards of beauty and, thus, may affect depression onset. This hypothesis is supported by the longitudinal study from Stice et al.  on female adolescents, in which body dissatisfaction has been identified as a predictor of depression. In this context, experiencing weight stigma predicts poor psychological outcomes including depression, similar to those outcomes who have been linked to higher BMI . On the other hand, an association between body image and depression is also supported by the findings from neurobiological investigations . Deficits in the hypothalamic pituitary-adrenal axis and serotonin system have been shown to be involved in mood disorders as well as in weight regulation. Furthermore, also brain areas which are involved in hedonic regulation may play a role for both body image and depression .
Our study has several strengths, including the large, nationally representative sample of individuals 18 years and older living in Switzerland, due to the use of weighting factors, which allows for the extrapolation of the results in relation to age, sex, region and nationality from the sample to the total population. Furthermore, the survey data allowed for adjusting for a number of important covariates associated with BWD and depression, although we were not able to take all potential confounders into consideration, such as family history of depression, medication, and also residual confounding might have occurred. A further strength was that depression was defined using a validated instrument with DSM-IV based criteria. However, our analysis was based on a cross-sectional study, and therefore we cannot exclude reverse causation, i.e. depression may also lead to BWD, which is a major limitation. Nevertheless, as these associations have not been examined yet for Switzerland, it is worthwhile to start with this population-based cross-sectional approach, but longitudinal studies are needed to examine the temporal relationship between body image and depression. Because institutionalized individuals were excluded from the sampling procedure, excluding most probably cases with severe depression, thus the prevalence of depression is possibly underestimated. The fact, that BWD, depression, body weight, height, and potential confounders were based solely on self-report may have biased the results. Finally, it should be noted that although BWD and body image dissatisfaction are related constructs, they are not redundant. The various aspects of body image and depression discussed in the present literature have therefore to be taken into consideration.