Food consumption frequency and perceived stress and depressive symptoms among students in three European countries

1475-2891-8-31 1475-2891 Research Food consumption frequency and perceived stress and depressive symptoms among students in three European countries Mikolajczyk T Rafael rmikolajczyk@uni-bielefeld.de El Ansari Walid walidansari@glos.ac.uk Maxwell E Annette amaxwell@ucla.edu

Department of Public Health Medicine, School of Public Health, University of Bielefeld, Germany

University of Gloucestershire, Faculty of Sport, Health & Social Care, Oxstalls Campus, Oxstalls Lane, Gloucester GL2 9HW, UK

School of Public Health and Jonsson Comprehensive Cancer Center, University of California, Los Angeles, USA

Nutrition Journal 1475-2891 2009 8 1 31 http://www.nutritionj.com/content/8/1/31 19604384 10.1186/1475-2891-8-31 17 11 2008 15 7 2009 15 7 2009 2009 Mikolajczyk et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

Certain foods might be more frequently eaten under stress or when higher levels of depressive symptoms are experienced. We examined whether poor nutritional habits are associated with stress and depressive symptoms and whether the relationships differ by country and gender in a sample from three European countries collected as part of a Cross National Student Health Survey.

Methods

A cross-sectional survey was conducted among first-year students in Germany (N = 696), Poland (N = 489) and Bulgaria (N = 654). Self-administered questionnaires included a 12-item food frequency questionnaire, Cohen's Perceived Stress Scale, and a modified Beck Depression Index. Linear regression analyses were conducted for two outcomes, perceived stress and depressive symptoms.

Results

Food consumption frequencies differed by country and gender, as did depressive symptoms and perceived stress. For male students, none of the food consumption groups were associated with perceived stress or depressive symptoms. In females, perceived stress was associated with more frequent consumption of sweets/fast foods and less frequent consumption of fruits/vegetables. Additionally, depressive symptoms were associated with less frequent consumption of fruits/vegetables and meat.

Conclusion

Our data show consistent associations between unhealthy food consumption and depressive symptoms and perceived stress among female students from three European countries, but not among male students. This suggests that efforts to reduce depressive symptoms and stress among female students may also lead to the consumption of healthier foods and/or vice-versa.

Introduction

Dietary habits are a major aspect of people's lifestyles that influence health, morbidity, and mortality for a range of conditions. Hence, patterns of food consumption and their relation to mental health have received some attention in research 1. For example, some observational and experimental studies explored the effects of carbohydrate intake on mood 234. Other studies have assessed the association between stress and food selection, reporting partly conflicting results 567891011. Carbohydrate consumption has been hypothesized to relieve depressive moods 12, and this has been considered as part of the causal link for developing obesity 1314. However, the association has also been seen in the opposite direction, with stress and depressive symptoms resulting in poorer food choices 15. Indeed, studies on the effects of stress on food choice show that people experiencing periods of stress reported overeating foods they would normally avoid, and that they ate these foods to feel better 16.

In children, stress was correlated with being overweight 1718, unhealthy eating behaviours, as well as with the use of eating as a coping mechanism 19. For adolescents of both genders in the U.S., the lack of a healthy diet was associated with reporting depression/stress for 10 or more days in the past month 20. Stress not only increased food consumption in certain individuals but also shifted their food choices from lower fat to higher fat foods 16.

Whilst eating has been theorized as a coping strategy for stressful situations 19, less is known about the association of stress or depression with the frequency of consumption of various food groups among college students 15. For instance in Germany, students preparing for exams had higher stress and more tendency to eat in order to distract themselves from stress than compared to control students 21. In the U.S., weight gain in college women was negatively associated with students being stress-free, eating vegetables, and consuming less high-cholesterol foods 22. Additionally, given that 65% of United Arab Emirates university students reported that their stress levels were too high and 50% reported that their diet was unhealthy 23, the importance of understanding students' patterns of consumption of food groups becomes evident. If poor nutritional habits are associated with stress and/or depressive symptoms, programs addressing mental health may also lead to the consumption of healthier foods and/or vice-versa.

Although depression is often related to appetite changes 24, little research has been done to examine the relationship between healthy eating and depressed mood 25. In fact, until recently, no studies had examined the relationship between depression and nutritional intake, e.g., among adolescents 25. Previous studies that examined this link usually focused on single countries, e.g., the U.S. 2526, the UK 27, or China 15. When single countries are examined, participants usually share the same underlying nutritional habits and other background characteristics that are potentially related to perceived stress or depressive symptoms. Single-country studies are also rarely directly comparable to one another due to the differences in measures of food consumption or mental health indicators. This has led to suggestions that future research on nutrition and on the correlation between depression and food consumption should be conducted across diverse student populations 15. University students are particularly important as they have greater freedom and control over their lifestyles, and health behaviours formed during young adulthood may have sustaining impacts on health throughout later life 28. Hence, it is of interest to assess the extent of association between indicators of mental health (such as perceived stress and depressive symptoms) and nutritional habits.

The aim of the analysis described in this paper is to assess the associations between mental health and nutritional habits across culturally diverse samples of students from three European countries. The analysis explores the links between reported levels of perceived stress and depressive symptoms and the consumption of selected food groups. The three samples consisted solely of first-year university students in each of the three countries; hence, sources of variability, such as education level or socio-economic status, are reduced.

Methods

Sample

The dataset used in this analysis is part of the Cross National Student Health Survey (CNSHS) 29, a general health survey among student populations conducted in several European countries. The current dataset is from three universities in three countries: University of Bielefeld, Germany (DE); Catholic University of Lublin, Poland (PL); and Sofia University, Bulgaria (BG). Papers related to depressive symptoms in these three countries have already been published 3031. The questionnaire was initially developed in German and then translated into Polish and Bulgarian using two independent translations for each language. Cases of disagreement were reviewed by the research team and decisions were made by the authors familiar with the respective languages (usually native speakers). Approval of the study and data collection at the three participating universities took place in 2005. The participating universities were selected based on the first author's appointment (University of Bielefeld) and working relationships with colleagues (Catholic University of Lublin; Sofia University). The protocol was the same across the three countries: first-year undergraduate students were invited to complete a self-administered questionnaire towards the end of a course lecture. The courses were selected to achieve a locally representative sample that was also comparable between the three sites, with one-third of students from each university coming from each of the three discipline areas: natural sciences, social sciences and language, and law and economy. Within each discipline area, courses were randomly selected until the expected quota was reached. We had planned to recruit about 500 students at each institution, but due to some large courses we exceeded this goal in Germany and Bulgaria. Students were informed about the study aims and that by completing a questionnaire they provided their informed consent to participate in the study. Participation was voluntary and anonymous, and withdrawal from the study was possible at any stage. Response rates varied among the sites: 85% in Germany and over 95% in both Poland and Bulgaria. The total number of respondents from the three sites was 2,103 students, although the current analysis is based on 1,839 (87%) respondents due to some missing values.

Variables

Assessment of dietary intake

Students completed a food frequency questionnaire (12 indicator variables) that measured their consumption of sweets, cakes/cookies, snacks and fast/canned food, fresh fruits, raw and cooked vegetables and salads, meat and fish, milk products, and cereals (see Table 1). The instrument was created to include food groups that are important when studying dietary habits, in line with other research studies 32. The introductory question, "How often do you eat the following foods?" asked participants about the frequency of their usual consumption of each food group separately (rated on a 5-point scale: several times a day, daily, several times a week, 1–4 times a month, and never). Both the face and content validity of the instrument were ascertained by grounding the questionnaire on literature review. No formal test of validity was performed, but the questionnaire was very similar to other food frequency questionnaires that had been validated, e.g., 3334.

Table 1

Food consumption and mental health indicators by country and gender

Female

Male

Female

Male

Female

Male

N = 394

N = 302

N = 351

N = 138

N = 449

N = 205

Food Group^a

Mean (SD)

Sweets

3.3 (1.0)

3.0 (1.0)

3.1 (0.9)

3.1 (0.8)

3.6 (0.9)

3.4 (0.9)

Cakes/cookies

2.3 (0.6)

2.2 (0.6)

2.8 (0.8)

2.7 (0.8)

3.1 (0.9)

3.0 (0.9)

Snacks

2.1 (0.7)

2.3 (0.7)

2.1 (0.8)

2.2 (0.9)

2.8 (0.9)

2.7 (0.8)

Fast food

2.2 (0.6)

2.4 (0.6)

1.8 (0.7)

2.0 (0.8)

3.1 (1.0)

3.5 (0.9)

Fresh fruits

3.5 (0.9)

3.2 (0.9)

3.3 (0.9)

3.0 (0.9)

3.6 (0.9)

3.3 (0.8)

Salad

3.3 (0.8)

3.1 (0.8)

3.0 (0.8)

3.7 (0.9)

3.4 (0.8)

Cooked vegetables

3.1 (0.8)

3.0 (0.8)

2.7 (0.9)

2.6 (0.9)

3.0 (0.9)

3.1 (0.9)

Soft drinks

2.5 (1.1)

2.9 (1.0)

2.9 (1.1)

3.1 (0.9)

2.9 (1.2)

3.3 (1.1)

Meat

3.0 (1.0)

3.6 (0.9)

3.3 (0.9)

3.6 (0.9)

3.1 (1.0)

3.7 (0.9)

Fish

2.0 (0.7)

2.2 (0.8)

2.2 (0.7)

2.3 (0.7)

2.5 (0.8)

Milk products

3.9 (0.9)

3.3 (1.0)

3.2 (1.0)

3.8 (0.8)

3.7 (0.9)

Cereal/cereal products

3.9 (0.9)

3.6 (1.1)

3.6 (1.0)

3.5 (1.1)

3.8 (1.1)

Mental Health Indicators

M-BDI^b

28.1 (15.6)

25.2 (14.7)

33.6 (17.4)

27.6 (15.2)

33.6 (15.4)

29.9 (13.6)

PSS^c

25.2 (8.1)

22.9 (8.0)

29.3 (7.5)

25.0 (6.9)

26.5 (7.8)

23.8 (7.3)

^aMean of the consumption frequency scale from 1 = never to 5 = several times per day

^bMean Modified Beck Depression Index, higher scores indicate stronger depressive symptoms

^cMean Perceived Stress Scale by Cohen, higher scores indicate higher perceived stress

Stress and depressive symptoms measures

Perceived stress was measured with Cohen's Perceived Stress Scale (PSS -14 items) 35, which assesses the extent to which a respondent considers life situations to be stressful. The questions measure how unpredictable, uncontrollable, and overloaded respondents find their lives, using a 5-point Likert scale response format ('0 = Never', '4 = Very Often'). Scores for individual participants were obtained by summing their responses to all 14 items. Employing the PSS scale in a population probability sample in the U.S., Cohen & Williamson 36 reported an internal reliability (Cronbach's alpha) of 0.78. The scale's predictive and discriminant validities were also established in studies that linked the measured concept of stress to health outcomes 3637. In our sample, Cronbach's alpha of the PSS was 0.85 in Germany, 0.81 in Poland, and 0.80 in Bulgaria 31.

Depressive symptoms were measured using a modification of the Beck Depression Inventory (M-BDI) 3839. The modification of the original BDI included two approaches: (a) the four items per symptom, which assessed the specific symptom's intensity in the original BDI, were replaced by a single statement per symptom with a six-point Likert scale measuring its frequency in the last 4 weeks (with the two extreme categories labelled as 0 = 'Never', 5 = 'Almost Always'); and (b) one symptom, which exhibited low specificity (loss of weight) was excluded. The reduction in the number of items per symptom is consistent with another recent modification of the BDI (BDI-II 40). The German language M-BDI, along with other versions of the BDI, computes a single score for individual respondents by summing their responses for all items of the scale. Through a German general population sample and in selected subsamples 3839, the authors of the M-BDI have demonstrated its construct validity and measurement equivalence as compared to the original BDI. The authors have also provided a cut-off score for screening for clinically relevant depressive symptoms at ≥ 35, corresponding to the 85th percentile of the representative sample of the German population 41. In our sample, Cronbach's alpha of M-BDI was 0.90 in Germany, 0.92 in Poland, and 0.87 in Bulgaria 31.

Statistical analysis

The analysis was conducted using SPSS 13, with statistical significance level set at p < 0.05. We present descriptive data on food consumption and mental health indicators (means and standard deviations of the item values) by country and gender. We assessed univariable associations between consumption of food groups and both mental health indicators using linear regression stratified by gender and adjusted for country. In order to reduce correlations between consumption of similar food groups, we built subscales for some food groups prior to adjusting for all food groups in the multivariable regression. Based on theoretical considerations regarding the content of foods, carbohydrate dense foods (sweets, cake/cookies, snacks, and fast food) were combined in one subscale; similarly, one subscale was created for fresh fruits and salads and cooked vegetables. This approach was supported by at least moderate correlations (Spearman rho >0.2) among the items of each subscale and factor analysis (results not shown). The subscales were created as mean scores of the corresponding items. The two new subscales and the remaining individual food groups were tested for multicollinearity with respect to the outcome variables. All variables displayed variance inflation factors far below 5, which could be an indication of serious multicollinearity problems 42. The independent associations between food groups and perceived stress and depressive symptoms were studied in two separate multivariable linear regression models. Given the gender and country differences across depressive symptoms, the analysis was stratified by gender and adjusted for country. Additionally, we included interaction terms to test whether the associations between specific food groups and mental health indicators differed across countries.

Results

Characteristics of the sample

Table 1 shows that 65.3% of the study sample was female. The country distribution of the students was 38% from Germany, 27% from Poland, and 35% from Bulgaria. Participants' average age was 20.6 years (SD = 2.3 years). About 2% of students in Germany, 22% in Bulgaria, and 56% in Poland were <20 years, with a very narrow age range in Poland and Bulgaria (data not shown).

Food consumption behaviour and mental health indicators

The frequency of food consumption differed by country and gender (Table 1). Consumption of sweets, cakes, snacks, and fast food was generally more common in Bulgaria than in Poland or Germany. In all countries, the consumption of sweets and cakes was more common in females than in males, and conversely, the consumption of fast foods was more common in males. Eating fresh fruits, salads and cooked vegetables, milk products, and cereals was only slightly more common in females, while the consumption of soft drinks/lemonade, meat, and fish was more common in males. Females displayed higher scores of depressive symptoms and perceived stress than males. There were also differences in depressive symptoms across countries.

Associations between food intake and perceived stress or depressive symptoms

The univariable associations are presented in Table 2. The similar associations between the consumption of sweets, cakes, snacks, and fast food and mental health indicators, and between the consumption of fruits, salads and vegetables and mental health indicators support our decision to combine these food groups into subscales. Because the association between the consumption of fast food and mental health indicators deviated from this pattern among male students, we conducted a more detailed analysis stratified by country and found that the effect existed only in Poland, while no significant associations were seen in Bulgaria and Germany.

Table 2

Associations between food consumption and perceived stress and depressive symptoms (each food group adjusted solely for country, separate models for males and females and for both mental health indicators)

Perceived Stress score (PSS)

Depressive Symptoms score (M-BDI)

Female

Male

Female

Male

Food group

p-value

Estimate*

p-value

Estimate*

p-value

Estimate*

p-value

Estimate*

Sweets

0.04

0.54

0.37

-0.31

0.27

0.59

0.10

-1.11

0.13

0.48

0.46

-0.30

0.79

0.17

0.27

-0.89

Snacks

0.04

0.66

0.92

0.04

0.33

0.62

0.34

-0.76

Fast food

0.07

0.55

0.04

0.84

0.57

0.34

0.02

1.85

Fruits

<0.001

-1.17

0.37

-0.32

0.002

-1.69

0.53

-0.45

Salads

<0.001

-1.21

0.23

-0.48

<0.001

-2.55

0.25

-0.88

Vegetables

0.003

-0.82

0.97

-0.01

0.003

-1.62

0.29

0.77

Soft drinks

0.52

-0.14

0.60

0.17

0.05

-0.90

0.55

-0.36

Meat

0.03

-0.52

0.80

0.09

0.003

-1.47

0.24

-0.78

Fish

<0.001

-1.32

0.75

-0.13

0.02

-1.60

0.90

0.10

Milk products

0.009

-0.72

0.34

-0.34

0.06

-1.07

0.08

-1.18

Cereal products

0.17

-0.33

0.17

-0.41

0.17

-0.67

0.07

-1.02

* Change in the corresponding score (PSS or M-BDI) per one unit of the food group frequency scale

In the multivariable analysis stratified by gender, the two-way interactions between countries and food groups were not statistically significant for either perceived stress or depressive symptoms, indicating a similar relationship between food intake and stress and between food intake and depressive symptoms. A single exception was an interaction between country and fish consumption with respect to depressive symptoms in females, with higher levels of depressive symptoms in females consuming more fish in Germany, lower levels of depressive symptoms in females consuming more fish in Bulgaria, and no association in Poland. Subsequently, the interaction terms were removed from both models and the country variable was retained in the analysis to adjust for confounding.

For male students, none of the food consumption subscales or food groups were associated with perceived stress or depressive symptoms (Table 3). In females, higher consumption of carbohydrate dense foods such as sweets, cookies, snacks, and fast food was associated with higher perceived stress, but not with depressive symptoms scores. A less frequent consumption of fruits and vegetables was associated with both higher perceived stress and depressive symptoms scores. (The partial eta square was nearly equal in both models, data not shown). Additionally, there was a negative association between meat consumption and depressive symptoms among females.

Table 3

Associations between food consumption and perceived stress and depressive symptoms (multivariable analysis adjusted for country and for all other variables in the table, separate models for males and females and for both mental health indicators)

Perceived Stress score (PSS)

Depressive Symptoms score (M-BDI)

Female

Male

Female

Male

Food group or subscale

p-value

Estimate*

p-value

Estimate*

p-value

Estimate*

p-value

Estimate*

Sweets/Cookies/Snacks/Fast food^#

0.03

0.72

0.29

-0.46

0.15

0.96

0.30

-0.89

Fruits/Vegetables⁺

<0.01

-1.17

0.43

-0.40

<0.01

-2.37

0.94

-0.07

Soft drinks

0.83

-0.05

0.23

0.40

0.16

-0.64

0.64

0.29

Meat

0.11

-0.40

0.91

0.04

0.01

-1.38

0.34

-0.66

Fish

0.06

-0.69

0.83

-0.09

0.95

-0.05

0.71

0.31

Milk products

0.12

-0.44

0.49

-0.26

0.23

-0.72

0.22

-0.87

Cereal products

0.99

0.00

0.38

-0.28

0.61

-0.26

0.17

-0.79

* Change in the corresponding score (PSS or M-BDI) per one unit of the food group frequency scale

** Sweets/cookies/Snacks/Fast food subscale: mean of four items (sweets, cakes/cookies, snacks, fast food)

⁺Fruits/Vegetables subscale: mean of three items (fresh fruits, salads, cooked vegetables)

Discussion

Today's college students are tomorrow's parents, role models, and patients. Unhealthy food practices and habits could impose health risks later in life and could be passed on to the next generation. Diet has an effect on mood 43, and although the emotional well being of university students has been studied 44, recent reports indicate that depressive symptoms in students are of principal importance and require further study 45. Our findings show that the relationships between food consumption and depressive symptoms and perceived stress were consistent across the studied countries but different by gender. While in males there was no association between consumption of food groups and the above-mentioned mental health indicators, the associations were quite strong in female students.

We found associations between the consumption of sweets/fast food and fruits/vegetables and perceived stress and between the consumption of fruits/vegetables and meat and depressive symptoms. The association between higher consumption of sweets and higher perceived stress levels was also reported by others: sweets, chocolate, cake, and biscuits were eaten more often under stress 846. Food composition (e.g., high fat/energy content) may influence people's selections of certain foods during life events that are stressful 46). On the other hand, stress might trigger a loss of control mechanisms by which people avert themselves from consuming perceived fattening or unhealthy foods 16. That "meal-type" foods, which often consist of salads or vegetables, are also eaten less frequently during periods of stress 8 might explain the observed negative correlation between fruits/vegetables and perceived stress.

Higher consumption of fruits/vegetables was associated lower levels of depressive symptoms among females in our study. The direction of this association seems to be due to the behavioural consequences of higher depressive symptoms and is consistent with the correlation between depressive symptoms and perceived stress 31. Interestingly, more frequent meat consumption was associated with lower levels of depressive symptoms in females. The interpretation of this finding is not entirely clear. Possibly, again the consumption of meat indicates better mood, rather than that meat positively affects mood.

Conversely, fish consumption (rich in omega-3 fatty acids) might be causally associated with mood stabilization 47, with some evidence that levels of these fatty acids are linked to depression 48. However, we did not find any association between fish consumption and depressive symptoms, consistent with Hakkarainen et al 49 who reported that dietary intake of omega-3 fatty acids showed no association with low mood level. Indeed, the evidence base on the relationships between fish consumption and depressive symptoms remains inconclusive. For instance Hakkarainen et al 50 found that subjects reporting anxiety or depressed mood had higher intake of omega-3 and omega-6 fatty acids – findings that conflict with previous reports of the beneficial effects of these fatty acids on mood, where lower prevalence of depressive symptoms was reported among people consuming high amounts of fish 5152. These conflicting findings probably reflect the different dietary intake levels of omega-3 fatty acids employed in different trials (ranging from 9.6 g/day, 47 to 2.2 g/day, 49), and the lack of distinction between consumption of white versus fatty fish, which have varying contents of fatty acids (0.48 g/100 g in white fish (cod) to 5.33 g/100 g in fatty fish (mackerel) 53.

While an increased consumption of sweets/fast food was associated with higher levels of perceived stress, the absence of this correlation for depressive symptoms might indicate that increased consumption partly relieves depressive symptoms. Carbohydrate ingestion has been hypothesized to relieve depressive moods 12, but such effects could be mediated through psychological factors rather than nutrient content of sweets 54. Hence future studies of the influence of carbohydrates on mood will need to consider people's pre-existing psychological and physiological functioning 2.

All the above findings were observed only in women. In males, none of the associations were significant and most of the estimates were closer to zero. The single exception was increased stress and depressive symptoms in Polish males with a more frequent fast food consumption observed in univariable analysis. Since the effect was restricted solely to Polish male students and not seen for male students in the other countries, and we are not aware of any theoretical justification, we see this as a chance finding. The association disappeared in multivariable analysis using the subscale for carbohydrate dense foods. Previous studies assessing the association of food intake with one or both mental health indicators in Chinese 15 and American 15 populations did not investigate the potential effect modification by gender, therefore the global associations they observed might have also resulted from associations limited to women only. Many individual, social, and political factors influence food selection and eating patterns 55. Hence, gender differences may result from different responses to perceived stress with respect to food consumption: either increased (hyperphagia) or decreased (hypophagia) and different prevalences of these responses by gender 8. Females, being more often restrained eaters 56, might react more strongly to perceived stress and/or depressive symptoms in their food intake. The preparation of healthy items (salads and cooked vegetables) might also require some additional efforts. Therefore under stress or decreased motivation due to depressive symptoms their consumption might decrease. Other explanations include female perceptions of self- and body-image and self-esteem, which have been associated with depression and might be associated with food consumption 5758.

Strengths and limitations

In all three countries, data were collected by the same method, and the treatment of the data was the same across sites. Since there may be regional variations and systematic differences between universities in each country, the data from single universities may not be representative for the countries included in this analysis. However, a high response rate at each site guaranteed that selection bias was not a likely threat to the internal validity of the study. Both mental health indicators and food consumption assessment were based on self-report and may be subject to social desirability bias. Furthermore, food frequency questionnaires do not assess serving sizes, which increases unmeasured variation, decreases precision, and possibly also affects validity of the measurement. When combining food groups into subscales, we assumed that students who eat only salads, for example, do not eat larger portions than students who eat salads, fruits, and vegetables. The food frequency questionnaire used in this study was not tested against objective and more sophisticated methods of food consumption measurement. Nevertheless, the instrument was similar to other food frequency questionnaires for which some proof of validity exist 3334. A further specific limitation is that we did not ask whether students ate at the university canteen/refectory or at their parental home. In both these cases, students may have less control over what they eat, especially at meal times.

Finally, given the cross-sectional nature of the study, we were not able to assess the direction of the association between food consumption and mental health. Given the absence of physiological mechanisms by which fruits or vegetables diminish perceived stress or depressive symptoms, it is most likely that the observed negative association resulted as effects of mental health on food consumption.

Conclusion

Using data from three European countries from a study with a common methodology, we showed an association between mental health indicators (perceived stress and depressive symptoms) and food intake in female, but not male, students. Our findings suggest that interventions oriented towards perceived stress and depressive symptoms in female students should also address the issue of healthy nutrition. Additionally, efforts to reduce depressive symptoms and stress among female students may lead to the consumption of healthier foods and/or vice-versa.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

RTM designed the research question, conducted the analysis and drafted the results and methods sections. WEL contributed to the research question and wrote the final manuscript. AEM participated in writing the manuscript.

Acknowledgements

The authors thank the reviewers for recommendations that significantly strengthened the article. In addition to the authors, the Cross National Students Health Study group includes: S Meier, A Kramer (Germany); H Ozcebe, DAslan (Turkey); J Klumbiene, I Miseviciene (Lithuania); S Ilieva (Bulgaria); C. Stock (Denmark); F Guillen-Grima (Spain) and others.

Mood and carbohydrate cravings Christensen L Pettijohn L Appetite 2001 36 137 145 10.1006/appe.2001.0390 11237349 Carbohydrate ingestion, blood glucose and mood Benton D Neurosci Biobehav Rev 2002 26 293 308 10.1016/S0149-7634(02)00004-0 12034132 The effects of nutrients on mood Benton D Donohoe RT Public Health Nutr 1999 2 403 409 10.1017/S1368980099000555 10610080 Food, mood and health: a neurobiologic outlook Prasad C Braz J Med Biol Res 1998 31 1517 1527 10.1590/S0100-879X1998001200002 9951546 Changes in plasma lipids and dietary intake accompanying shifts in perceived workload and stress McCann BS Warnick GR Knopp RH Psychosom Med 1990 52 97 108 2305026 Relationships between a critical life event and eating behavior in highschool students Michaud C Kahn JP Musse N Burlet C Nicolas JP MeJean L Stress Med 1990 6 57 64 10.1002/smi.2460060112 The effects of academic stress on health behaviors in young adults Weidner G Kohlmann CV Dotzauer E Burns LR Anxiety Stress Coping 1996 9 123 133 10.1080/10615809608249396 Perceived effects of stress on food choice Oliver G Wardle J Physiol Behav 1999 66 511 515 10.1016/S0031-9384(98)00322-9 10357442 Effects of academic examination stress on eating behavior and blood lipid levels Pollard TM Steptoe A Canaan L Davies GJ Wardle J Int J Behav Med 1995 2 299 320 10.1207/s15327558ijbm0204_2 16250770 Anxiety and food intake in men Bellisle F Louis-Sylvestre J Linet N Rocaboy B Dalle B Cheneau F L'Hinoret D Guyot L Psychosom Med 1990 52 452 457 2399296 The stress-eating paradox: multiple daily measurements in adult males and females Stone AA Brownell K Psychol Health 1994 9 425 436 10.1080/08870449408407469 Carbohydrates and depression Wurtman RJ Wurtman JJ Sci Am 1989 260 68 75 2642626 Binge eating among the obese: a descriptive study Arnow B Kenardy J Agras WS J Behav Med 1992 15 155 170 10.1007/BF00848323 1583679 Changes in mood after carbohydrate consumption among obese individuals Liberman HR Wurtman JJ Chew B Am J Clin Nutr 1986 44 772 778 3788829 Perceived stress, depression and food consumption frequency in the college students of China Seven Cities Liu C Xie B Chou CP Koprowski C Zhou D Palmer P Sun P Guo Q Duan L Sun X Anderson Johnson C Physiol Behav 2007 92 748 754 10.1016/j.physbeh.2007.05.068 17585967 Food selection changes under stress Zellner DA Loaiza S Gonzalez Z Pita J Morales J Pecora D Wolf A Physiol Behav 2006 87 789 793 10.1016/j.physbeh.2006.01.014 16519909 Psychological stress and obesity Koch FS Sepa A Ludvigsson J J Pediatr 2008 153 839 844 10.1016/j.jpeds.2008.06.016 18657829 Child-specific food insecurity and overweight are not associated in a sample of 10- to 15-year-old low-income youth Gundersen C Lohman BJ Eisenmann JC Garasky S Stewart SD J Nutr 2008 138 371 378 18203906 Barriers that influence eating behaviors in adolescents Jenkins S Horner SD J Pediatr Nurs 2005 20 258 267 10.1016/j.pedn.2005.02.014 16030505 Association of adolescent risk behaviors with mental health symptoms in high school students Brooks TL Harris SK Thrall JS Woods ER J Adolesc Health 2002 31 240 246 10.1016/S1054-139X(02)00385-3 12225736 The perceived function of eating is changed during examination stress: a field study Macht M Haupt C Ellgring H Eat Behav 2005 6 109 112 10.1016/j.eatbeh.2004.09.001 15598596 Predicting 1-year change in body mass index among college students Adams T Rini A J Am Coll Health 2007 55 361 365 10.3200/JACH.55.6.361-366 17517548 Health and lifestyle needs assessment of medical students in the United Arab Emirates Carter AO Elzubeir M Abdulrazzaq YM Revel AD Townsend A Med Teach 2003 25 492 496 10.1080/01421590310001605633 14522670 American Psychological Association Diagnostic and statistical manual of mental disorders Washington, DC: APA 4 1994 Depressive symptoms and adolescent eating and health behaviors: a multifaceted view in a population-based sample Fulkerson JA Sherwood NE Perry CL Neumark-Sztainer D Story M Prev Med 2004 38 865 875 10.1016/j.ypmed.2003.12.028 15193910 Effects of coping style and negative body image on eating disturbance Koff E Sangani P Int J Eat Disord 1997 22 51 56 10.1002/(SICI)1098-108X(199707)22:1<51::AID-EAT6>3.0.CO;2-1 9140735 Stress, coping, and disturbed eating attitudes in teenage girls Fryer S Waller G Kroese BS Int J Eat Disord 1997 22 427 436 10.1002/(SICI)1098-108X(199712)22:4<427::AID-EAT8>3.0.CO;2-O 9356891 Predictors of health behaviours in college students Von Ah D Ebert S Ngamvitroj A Park N Kang DH J Adv Nurs 2004 48 463 474 10.1111/j.1365-2648.2004.03229.x 15533084 Promoting public health: benefits and challenges of a Europeanwide research consortium on student health El Ansari W Maxwell AE Mikolajczyk RT Stock C Naydenova V Kramer A Cent Eur J Public Health 2007 15 58 65 17645218 Prevalence of depressive symptoms in university students from Germany, Denmark, Poland and Bulgaria Mikolajczyk RT Maxwell AE El Ansari W Naydenova V Stock C Ilieva S Dudziak U Nagyova I Soc Psychiatry Psychiatr Epidemiol 2008 43 105 112 10.1007/s00127-007-0282-0 18038173 Depressive symptoms and perceived burdens related to being a student: Survey in three European countries Mikolajczyk RT Maxwell AE Naydenova V Meier S El Ansari W Clin Pract Epidemol Ment Health 2008 4 19 2483702 18598340 10.1186/1745-0179-4-19 Gender differences in health habits and in motivation for a healthy lifestyle among Swedish university students von Bothmer MI Fridlund B Nurs Health Sci 2005 7 107 118 10.1111/j.1442-2018.2005.00227.x 15877687 The validity of a short food frequency questionnaire and its ability to measure changes in food intake: a longitudinal study Osler M Heitmann BL Int J Epidemiol 1996 25 1023 1029 10.1093/ije/25.5.1023 8921490 Reproducibility of a short semi-quantitative food group questionnaire and its performance in estimating nutrient intake compared with a 7-day diet diary in the Million Women Study Roddam AW Spencer E Banks E Beral V Reeves G Appleby P Barnes I Whiteman DC Key TJ Public Health Nutr 2005 8 201 213 10.1079/PHN2004676 15877913 A global measure of perceived stress Cohen S Kamarck T Mermelstein R J Health Soc Behav 1983 24 385 10.2307/2136404 6668417 Cohen S Williamson G Perceived stress on a probability sample of the United States Newbury Park, CA: SAGE 1988 Sociability and susceptibility to the common cold Cohen S Doyle WJ Turner R Alper CM Skoner DP Psychol Sci 2003 14 389 395 10.1111/1467-9280.01452 12930466 Messgüte des vereinfachten Beck-Depressions-Inventars (BDI-V) Schmitt M Beckmann M Dusi D Maes J Schiller A Schonauer K Diagnostica 2003 49 147 156 10.1026//0012-1924.49.4.147 Vorschlag zur Vereinfachung des Beck-Depressions-Inventars (BDI) Schmitt M Maes J Diagnostica 2000 46 38 46 10.1026//0012-1924.46.1.38 Comparison of Beck Depression Inventories -IA and -II in psychiatric outpatients Beck AT Steer RA Ball R Ranieri W J Pers Assess 1996 67 588 597 10.1207/s15327752jpa6703_13 8991972 Normwerte für das Vereinfachte Beck-Depressions-Inventar (BDI-V) in der Allgemeinbevölkerung Schmitt M Altstöter-Gleich C Hinz A Maes J Brähler E Diagnostica 2006 52 51 59 10.1026/0012-1924.52.2.51 A Caution Regarding Rules of Thumb for Variance Inflation Factors O'Brien RM Quality and Quantity 2007 41 673 690 10.1007/s11135-006-9018-6 A healthy body, a healthy mind: long-term impact of diet on mood and cognitive function Rogers PJ Proc Nutr Soc 2001 60 135 143 10.1079/PNS200061 11310419 Psychiatric problems of medical students Saslow G J Med Educ 1956 31 27 33 13286651 An evaluation of depressed mood in two classes of medical students Levine RE Litwins SD Frye AW Acad Psychiatry 2006 30 235 237 10.1176/appi.ap.30.3.235 16728770 Stress influences appetite and comfort food preferences in college women Kandiah J Yake M Jones J Meyer M Nutrition Research 2006 26 118 123 10.1016/j.nutres.2005.11.010 Omega 3 fatty acids in bipolar disorder: a preliminary double-blind, placebo-controlled trial Stoll AL Severus WE Freeman MP Rueter S Zboyan HA Diamond E Cress KK Marangell LB Arch Gen Psychiatry 1999 56 407 412 10.1001/archpsyc.56.5.407 10232294 Omega-3 fatty acids in psychiatry: a review Freeman MP Ann Clin Psychiatry 2000 12 159 165 10984006 Is low dietary intake of omega-3 fatty acids associated with depression? Hakkarainen R Partonen T Haukka J Virtamo J Albanes D Lonnqvist J Am J Psychiatry 2004 161 567 569 10.1176/appi.ajp.161.3.567 14992986 Food and nutrient intake in relation to mental wellbeing Hakkarainen R Partonen T Haukka J Virtamo J Albanes D Lonnqvist J Nutr J 2004 3 14 519023 15363099 10.1186/1475-2891-3-14 Fish consumption, depression, and suicidality in a general population Tanskanen A Hibbeln JR Hintikka J Haatainen K Honkalampi K Viinamaki H Arch Gen Psychiatry 2001 58 512 513 10.1001/archpsyc.58.5.512 11343534 Fish consumption and self-reported physical and mental health status Silvers KM Scott KM Public Health Nutr 2002 5 427 431 10.1079/PHN2001308 12003654 Fatty Acids. Supplement to McCance & Widdowson's The Composition of Foods Cambrigde: Royal Society of Chemistry/Ministry of Agriculture, Fisheries and Food 1999 The effects of carbohydrate on arousal Reid M Hammersley R Nutr Res Rev 1999 12 1 23 10.1079/095442299108728901 19087444 Changes in vegetable and fruit consumption and awareness among US adults: results of the 1991 and 1997 5 A Day for Better Health Program surveys Stables GJ Subar AF Patterson BH Dodd K Heimendinger J Van Duyn MA Nebeling L J Am Diet Assoc 2002 102 809 817 10.1016/S0002-8223(02)90181-1 12067046 Gender differences in eating behavior and body weight regulation Rolls BJ Fedoroff IC Guthrie JF Health Psychol 1991 10 133 142 10.1037/0278-6133.10.2.133 2055211 Weight, weight-related aspects of body image, and depression in early adolescent girls Rierdan J Koff E Adolescence 1997 32 615 624 9360735 Explanations for female excess psychosomatic symptoms in adolescence: evidence from a school-based cohort in the West of Scotland Sweeting HN West PB Der GJ BMC Public Health 2007 7 298 2233615 17953744 10.1186/1471-2458-7-298