Glancing back over recent research studies that I have noticed & downloaded to my personal database, I was struck by a whole series on the effects of diet on psychological state.  I've listed twelve that caught my eye in the last several months - this first of two posts details studies that focus more on overall dietary quality.  The second post in the series focuses more on specific dietary components & psychological disorder.  There are obviously lots of interesting developments in this important area.

I wrote a couple of posts last autumn about "food & mood" - "Emerging research on diet suggests it's startlingly important in the prevention of anxiety & depression" and "So what dietary advice should we be following - for psychological as well as physical health?".  Now the same research team has published an important prospective study - Akbaraly, T. N., S. Sabia, et al. (2013). "Adherence to healthy dietary guidelines and future depressive symptoms: Evidence for sex differentials in the Whitehall II study." Am J Clin Nutr 97(2): 419-427.   "(Free full text available) Background: It has been suggested that dietary patterns are associated with future risk of depressive symptoms. However, there is a paucity of prospective data that have examined the temporality of this relation.  Objective: We examined whether adherence to a healthy diet, as defined by using the Alternative Healthy Eating Index (AHEI), was prospectively associated with depressive symptoms assessed over a 5-y period.  Design: Analyses were based on 4215 participants in the Whitehall II Study. AHEI scores were computed in 1991-1993 and 2003-2004. Recurrent depressive symptoms were defined as having a Center for Epidemiologic Studies Depression Scale score ≥16 or self-reported use of antidepressants in 2003-2004 and 2008-2009.  Results: After adjustment for potential confounders, the AHEI score was inversely associated with recurrent depressive symptoms in a dose-response fashion in women (P-trend < 0.001; for 1 SD in AHEI score; OR: 0.59; 95% CI: 0.47, 0.75) but not in men. Women who maintained high AHEI scores or improved their scores during the 10-y measurement period had 65% (OR: 0.35%; 95% CI: 0.19%, 0.64%) and 68% (OR: 0.32%; 95% CI: 0.13%, 0.78%) lower odds of subsequent recurrent depressive symptoms than did women who maintained low AHEI scores. Among AHEI components, vegetable, fruit, trans fat, and the ratio of polyunsaturated fat to saturated fat components were associated with recurrent depressive symptoms in women.  Conclusion: In the current study, there was a suggestion that poor diet is a risk factor for future depression in women."  In the discussion section of the paper, the authors write "The reason that this gradient was apparent in women but not men was unclear. One possible explanation, although nontestable with the current data set, was that the instrument we used to assess DepSs (depressive symptoms) was less sensitive to male depression; some CES-D items have been shown to produce biased responses in comparisons of male and female respondents (27). Therefore, additional prospective studies that use a clinical interview or other sensitive measures to detect depression both in men and women are needed."

Somewhat similar findings - poor dietary quality being linked to increased risk of subsequent depression - were also reported in last year's paper Jacka, F. N., C. Rothon, et al. (2012). "Diet quality and mental health problems in adolescents from East London: A prospective study" Soc Psychiatry Psychiatr Epidemiol.  "PURPOSE: In this study, we aimed to examine the relationship between diet quality and depression in a prospective study of adolescents from varied ethnic and cultural backgrounds. DESIGN: In this prospective cohort study, data were collected at two time points (2001 and 2003) from nearly 3,000 adolescents, aged either 11-12 years or 13-14 years, participating in RELACHS, a study of ethnically diverse and socially deprived young people from East London in the UK. Diet quality was measured from dietary questionnaires, and mental health assessed using the Strengths and Difficulties Questionnaire (SDQ) and the Short Mood and Feelings Questionnaire (SMFQ).  RESULTS: In cross-sectional analyses, we found evidence for an association between an unhealthy diet and mental health problems. Compared to those in the lowest quintile of Unhealthy diet score, those in the highest quintile were more than twice as likely to be symptomatic on the SDQ (OR 2.10, 95 %CI 1.38-3.20) after taking all identified confounders into account. There was also some evidence for a cross-sectional inverse association between a measure of healthy diet and mental health problems. A prospective relationship between the highest quintiles of both Healthy (OR 0.63, 95 %CI 0.38-1.05) and Unhealthy (OR 1.75, 95 %CI 1.00-3.06) diet scores and SDQ scores at follow-up was also evident, but was attenuated by final adjustments for confounders. CONCLUSION: This study is concordant with previous observational studies in describing relationships between measures of diet quality and mental health problems in adolescents."

And another dietary risk factor for the development of subsequent depression in young people was highlighted in Sanchez-Villegas, A., A. E. Field, et al. (2013). "Perceived and actual obesity in childhood and adolescence and risk of adult depression" J Epidemiol Community Health 67(1): 81-86.  "BACKGROUND: Obesity in childhood and adolescence has important health consequences, but its relation to risk of adult depression remains uncertain. OBJECTIVE: To examine the effect of perceived and actual obesity during childhood and adolescence on prevalence and incidence of adult depression risk. METHODS: Cohort study of 91,798 female registered nurses followed longitudinally for 12 years. RESULTS: As compared with lean women of the same age, women in the two highest categories of body shape at age 10 had both higher prevalence (OR=2.59, 95% CI 1.46 to 4.61) and incidence (OR=2.01, 95% CI 1.08 to 3.71) of depression. Similar results were obtained for body shape at age 20 (OR=3.43 for prevalence and OR=2.03 for incidence) and for body mass index (BMI) at age 18 (OR=2.92 for BMI >/= 40 kg/m(2)). These associations remained significant after adjustment for multiple confounders. CONCLUSION: These results indicate that childhood-adolescence obesity is a strong and independent risk factor for adult depression."

On the sunnier side we had Ford, P. A., K. Jaceldo-Siegl, et al. (2013). "Intake of Mediterranean foods associated with positive affect and low negative affect." Journal of Psychosomatic Research 74(2): 142-148. "Objective To examine associations between consumption of foods typical of Mediterranean versus Western diets with positive and negative affect. Nutrients influence mental states yet few studies have examined whether foods protective or deleterious for cardiovascular disease affect mood. Methods Participants were 9255 Adventist church attendees in North America who completed a validated food frequency questionnaire in 2002-6. Scores for affect were obtained from the Positive and Negative Affect Schedule questionnaire in 2006-7. Multiple linear regression models controlled for age, gender, ethnicity, BMI, education, sleep, sleep squared (to account for high or low amounts), exercise, total caloric intake, alcohol and time between the questionnaires. Results Intake of vegetables (β = 0.124 [95% CI 0.101, 0.147]), fruit (β = 0.066 [95% CI 0.046, 0.085]), olive oil (β = 0.070 [95% CI 0.029, 0.111]), nuts (β = 0.054 [95% CI 0.026, 0.082]), and legumes (β = 0.055 [95% CI 0.032, 0.077]) were associated with positive affect while sweets/desserts (β = - 0.066 [95% CI - 0.086, - 0.046]), soda (β = - 0.025 [95% CI - 0.037, - 0.013]) and fast food frequency (β = - 0.046 [95% CI - 0.062, - 0.030]) were inversely associated with positive affect. Intake of sweets/desserts (β = 0.058 [95% CI 0.037, 0.078]) and fast food frequency (β = 0.052 [95% CI 0.036, 0.068]) were associated with negative affect while intake of vegetables (β = - 0.076 [95% CI - 0.099, - 0.052]), fruit (β = - 0.033 [95% CI - 0.053, - 0.014]) and nuts (β = - 0.088 [95% CI - 0.116, - 0.060]) were inversely associated with negative affect. Gender interacted with red meat intake (P &lt; .001) and fast food frequency (P &lt; .001) such that these foods were associated with negative affect in females only. Conclusions Foods typical of Mediterranean diets were associated with positive affect as well as lower negative affect while Western foods were associated with low positive affect in general and negative affect in women."

And it was good to see stress-orientated interventions beginning to take lifestyle factors on board as important ingredients of treatment programmes - Casanas, R., R. Catalan, et al. (2012). "Effectiveness of a psycho-educational group program for major depression in primary care: A
randomized controlled trial" BMC Psychiatry 12: 230. "(Free full text available) ABSTRACT: BACKGROUND: Studies show the effectiveness of group psychoeducation in reducing symptoms in people with depression. However, few controlled studies that have included aspects of personal care and healthy lifestyle (diet, physical exercise, sleep) together with cognitive-behavioral techniques in psychoeducation are proven to be effective.The objective of this study is to assess the effectiveness of a psychoeducational program, which includes aspects of personal care and healthy lifestyle, in patients with mild/moderate depression symptoms in Primary Care (PC). METHODS: In a randomized, controlled trial, 246 participants over 20 years old with ICD-10 major depression were recruited through nurses/general practitioners at 12 urban Primary Care Centers (PCCs) in Barcelona. The intervention group (IG) (n=119) received a group psychoeducational program (12 weekly, 1.5 h sessions led by two nurses) and the control group (CG) (n=112) received usual care. Patients were assessed at baseline and at, 3, 6 and 9 months. The main outcome measures were the BDI, EQ-5D and remission based upon the BDI. RESULTS: 231 randomized patients were included, of whom 85 had mild depression and 146 moderate depression. The analyses showed significant differences between groups in relation to remission of symptoms, especially in the mild depression group with a high rate of 57% (p=0.009) at post-treatment and 65% (p=0.006) at 9 month follow up, and only showed significant differences on the BDI at post-treatment (p=0.016; effect size Cohen's d'=.51) and at 6 and 9 month follow-up (p= 0.048; d'=.44). In the overall and moderate sample, the analyses only showed significant differences between groups on the BDI at post-treatment, p=0.02 (d'=.29) and p=0.010 (d'=.47), respectively. The psychoeducation group improved significantly on the EQ-5D at short and long-term. CONCLUSIONS: This psychoeducational intervention is a short and long-term effective treatment for patients with mild depression symptoms. It results in a high remission rate, is recommended in PC and can be carried out by nurses with previous training. In moderate patients, group psychoeducation is effective in the short-term."

And good to have an expert, cautious, balanced view of where this area of diet & mood currently is in research terms - Sanchez-Villegas, A. and M. Martinez-Gonzalez (2013). "Diet, a new target to prevent depression?"  BMC Medicine 11(1): 3.  "(Available in free full text): BACKGROUND: Research on the role of diet in the prevention of depression is scarce. Some evidence suggests that depression shares common mechanisms with cardiovascular disease.  DISCUSSION: Before considering the role of diet in the prevention of depression, several points need to be considered. First, in general, evidence has been found for the effects of isolated nutrients or foods, and not for dietary patterns. Second, most previous studies have a cross-sectional design. Third, information is generally collected though questionnaires, increasing the risk of misclassification bias. Fourth, adequate control of confounding factors in observational studies is mandatory.  SUMMARY: Only a few cohort studies have analyzed the relationship between overall dietary patterns, such as the Mediterranean diet, and primary prevention of depression. They have found similar results to those obtained for the role of this dietary pattern in cardiovascular disease. To confirm the findings obtained in these initial cohort studies, we need further observational longitudinal studies with improved methodology, as well as large randomized primary prevention trials, with interventions based on changes in the overall food pattern, that include participants at high risk of mental disorders."