The relationship between the World Index for Sustainability and Health (WISH) score and mental health in women: a cross-sectional study

Diet quality has been associated with mental health, and recently, there has been growing interest in the association between the sustainability of diets and human health. The objective of this cross-sectional study was to explore the relationship between a newly developed dietary index for health and sustainability and psychological disorders among Iranian women. Participants in this cross-sectional study included 479 women living in Tehran with no history of chronic disease. A validated 168-item FFQ was used to assess dietary intake. The World Index for Sustainability and Health was calculated, consisting of four sub-scores: less healthy, healthy, low environmental impact and high environmental impact. Participants' psychological status was assessed using the Depression Anxiety Stress Scale-21. Logistic regression models were used to examine the association between the World Index for Sustainability and Health and psychological disorders. Participant ages ranged from 20 to 50 years, with a mean age of 31<middle dot>86 (sd 7<middle dot>68) years. After adjusting for potential confounders (age, energy, BMI, marital status, education, family history of chronic disease, body satisfaction, socio-economic status, physical activity, smoking), women in the highest tertile of the healthy sub-score had significantly lower odds of experiencing depression (OR 0<middle dot>40; 95 % CI 0<middle dot>24, 0<middle dot>67), anxiety (OR 0<middle dot>45; 95 % CI 0<middle dot>23, 0<middle dot>87) and psychological distress (OR 0<middle dot>46; 95 % CI 0<middle dot>28, 0<middle dot>77) compared with the reference group. Similarly, the less healthy sub-score was significantly associated with depression (OR 0<middle dot>51; 95 % CI 0<middle dot>32, 0<middle dot>89), anxiety (OR 0<middle dot>44; 95 % CI 0<middle dot>25, 0<middle dot>78) and psychological distress (OR 0<middle dot>57; 95 % CI 0<middle dot>36, 0<middle dot>90). An inverse association was observed between the low environmental impact sub-score and depression (OR 0<middle dot>32; 95 % CI 0<middle dot>19, 0<middle dot>54), anxiety (OR 0<middle dot>38; 95 % CI 0<middle dot>18, 0<middle dot>76) and psychological distress (OR 0<middle dot>30; 95 % CI 0<middle dot>17, 0<middle dot>51). However, no further significant associations were found with the high environmental impact sub-score, except with depression (OR 0<middle dot>57; 95 % CI 0<middle dot>33, 0<middle dot>96). The healthy and low environmental impact sub-scores of the World Index for Sustainability and Health were found to be inversely associated with depression, anxiety and psychological distress. However, due to the cross-sectional study design, causality cannot be inferred. Further prospective studies are required to validate and expand upon these findings and explore potential mechanisms and alternative explanations, such as reverse causation. While this study suggests that choosing a diet that is both healthy for individuals and sustainable for the environment may be associated with a lower risk of mental health issues among women, more research is needed.