This post explores the current evidence regarding potential connections between diet, anxiety and depression. What are the claims? What are the current research findings? If a connection exists, what are the implications for treatment?
Background: Anxiety and depression
What is anxiety?
Anxiety is defined as follows: “Anxiety is a feeling of nervousness, worry, or unease that is a normal human experience. It is also present in a wide range of psychiatric disorders, including generalized anxiety disorder, panic disorder, and phobias. Although each of these disorders is different, they all feature distress and dysfunction specifically related to anxiety and fear” (Barnhill, 2019, para 1).
While everyone experiences anxiety at times, it is considered a disorder if it occurs frequently, at times that are not appropriate, and interferes with a person’s normal activities (Barnhill, 2019). One in five Americans experience anxiety disorders annually, and nearly one in three will experience an anxiety disorder during their lifetime (National Institute of Mental Health, 2017).
Causes are believed to include (Barnhill, 2019):
- Genetic predispositions
- Psychological make up
- Health conditions
- Various substances such as alcohol, drugs, and stimulants
What is depression?
Depression is defined as: “a feeling of sadness intense enough to interfere with functioning and/or a decreased interest or pleasure in activities. It may follow a recent loss or other sad event but is out of proportion to that event and lasts beyond an appropriate length of time” (Coryell, 2019, para 1). Major depression affects approximately 7% of the U.S. population (National Institute of Mental Health, 2019).
Causes are believed to include (Coryell, 2019):
- Genetic predispositions
- Hormonal imbalances
- Health conditions
- Emotionally traumatic events
Current treatment approaches for depression and anxiety
Standard treatment approaches according to the Anxiety and Depression Association of America (2018) include:
- Psychotherapy approaches
- Social support
- Meditation, breathing exercises and relaxation techniques
- Physical exercises
But what about diet approaches? What role does diet play in contributing to depression and anxiety symptoms? Is there a role might diet play in treating these symptoms? What does the current evidence say?
What does the current evidence say about diet and its relation to depression / anxiety?
There has been growing interest in the connection between negative mood states and nutritional intake patterns in recent years. Intervention trials where single nutrients (such as supplements) were used to treat depression have been unable to provide convincing or consistent results (Lai, Hiles, Bisquera, Hure, McEvoy, & Attia, 2014). Nutrient supplements fail to factor for the complex relation between a massive array of nutrients found in whole foods and their combined effects interacting within the human body.
Research supports a relationship between your diet patterns and your risk of depression and anxiety
Research using the systematic review and meta-analysis method (where multiple studies are combined together to determine overall patterns) combined 21 studies overall examining dietary patterns and depression association (Lai et al., 2014). Findings noted that overall, persons consuming higher amounts of fish, fruits, vegetables and whole grains were significantly less likely to experience depression or symptoms characteristic of depression versus those who ate lower percentages of these items. The research, however, lacked controlled trials excepting one. There were some contradictory findings among the 21 studies.
In a separate meta-analysis combining 9 studies, high adherence to a Mediterranean diet was associated with a 32% reduction in depression occurrence (Psaltopoulou, Sergentanis, Panagiotakos, Sergentanis, Kosti, & Scarmeas, 2013). A Mediterranean diet is mostly plant-based: high in fruits, whole grains, vegetables and fish while also allowing for a lesser intake of eggs, dairy and poultry. There was a dose effect, where moderate adherence also produced a reduction in depression occurrences, though to a lesser extent versus high adherence. The study authors noted that protection against depression persisted despite increased age for those that most closely followed the Mediterranean diet versus those that did not.
Adherence to a western style diet is an independent predictor of having increased anxiety or depression (O’Neil at al., 2014). A western diet is high in refined carbs white rice, white bread/ white rolls, sugar, processed meats like hamburger, bacon, and lunch meats, as well as low fruit and vegetable intake. It is no coincidence that the standard American diet is abbreviated SAD in the medical literature!!
It is posited that lower inflammation in the brain and improved antioxidant protection of the brain may contribute to decreased depression symptoms (Lai et al., 2014; O’Neil et al., 2014). Skeptics have argued that the apparent relationship may just be based on happier, healthier persons being more motivated to eat healthier foods. However, research conducted over long periods of time (longitudinal research) is increasingly demonstrating a protective role healthy diets play in reducing anxiety and depression occurrence rates (O’Neil et al., 2014).
A more nutritious diet increases a person’s intake of magnesium, folate, omega 3 fatty acids, and zinc…these have been associated with lower depression and anxiety rates (O’Neil et al., 2014). Research has noted that depressed people often have higher levels of inflammation than non-depressed persons. Poor quality diets (high in sugar and fat) appear to inhibit formation of a brain protein used in nerve cell health, maintenance and communication. Lower levels of this protein–brain-derived neurotrophic factor–have been associated with depression (O’Neil et al., 2014).
Note: for those opting for an exclusively plant-based diet, a non-fish option for the marine form of omega 3 fatty acids (DHA), algae oil is an alternative. One example can be found here.
Mental health in children and adolescents appears to be connected to dietary patterns as well
A systematic review was conducted combining results from 12 high quality studies, inclusive of more than 80,000 children and adolescents (O’Neil et al, 2014). Results found that as diet quality declined, so did overall mental wellness in children and adolescents. The opposite trend occurred as well, with high quality diets increasingly associated with better mental health in children and adolescents. However, the research was somewhat conflicting and failed to determine cause and effect (O’Neil et al., 2014). Did the children feel bad, so in turn they ate poor quality foods like sweets, etc? Or did eating bad make them feel bad? A different style of research is needed to answer that question.
What happens when you put people with depression on a healthy diet?
To answer the question of cause (healthy diet) and effect (improved mental health), a study was performed using the “gold standard” randomized controlled trial taking persons diagnosed with major depressive disorder and giving a group of them a healthy diet (Jacka et al., 2017). The healthy diet in this study was the Mediterranean diet as described above over a 12 week period. Results were compared against another group who simply received standard medical treatment and a social support intervention. All participants were confirmed to follow a poor diet prior to the study. Further, they were to make no changes to their routine treatment regimen in terms of medications and psychotherapy prior to the study.
During the 12 week trial, 31 persons with depression followed the Mediterranean diet, while 25 persons received social support but made no changes to their diet. The group following the Mediterranean diet as an intervention for their depression showed significant improvement with an impressive effect size (i.e.- the effect was not simply a mild improvement but rather, a substantial improvement) (Jacka et al., 2017). This improvement was significantly better than the improvement experienced by those receiving social report but having no diet change.
In fact, 10 of the 31 persons in the group following the Mediterranean diet achieved reduction of symptoms to the extent that their depression was considered to be in remission, versus only 2 of the 25 persons receiving social support (Jacka et al., 2017). There was also a significant reduction of anxiety symptoms for those following the healthy diet with a moderate effect size (showing the improvement was more than just a small improvement).
Other interesting facts were noted during this research. The cost of the healthier diet was matched against spending patterns of participants prior to the study for food. The healthy diet actually averaged LOWER in cost than what participants were spending on their unhealthy diets prior to the study! Finally, participants were matched in both groups for BMI, self-efficacy, smoking rates and physical activity, showing that the difference experienced is best explained by the dietary intervention. Limits of the study included a small sample size (56 participants).
Research is increasingly demonstrating an interplay between diet and depression and anxiety. Poor diets high in refined carbohydrates such as sugar, white bread, white rice, fatty foods and meats appear to worsen symptoms. Higher quality diets consisting of high intakes of fruits, vegetables, whole grains, lean proteins and fish appear to reduce symptoms.
The fact that diet does not appear to work for all circumstances, nor does it appear to be a cure necessarily is consistent with research demonstrating depression and anxiety occurrence being due to multiple factors. However, the improvements that can be experienced by persons suffering from anxiety and depression when following a healthy diet can be impressive!! Persons suffering from anxiety and depression may not be able to control factors such as genetics or current life circumstances.
A healthy diet, however, may be something within control for sufferers of these debilitating disorders. A healthy diet appears to be a low cost and effective complementary treatment approach for those suffering with anxiety and depression. In fact, the growing research begs the question, WHY WOULDN’T this be a PART of the standard treatment approach?? The evidence suggests It absolutely needs to be in my view!
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Anxiety and Depression Association of America. (2018). Treatment. Retrieved from https://adaa.org/understanding-anxiety/depression/treatment
Barnill, J. W. (2019). Overview of anxiety disorders. Retrieved from https://www.merckmanuals.com/home/mental-health-disorders/anxiety-and-stress-related-disorders/overview-of-anxiety-disorders
Coryell, W. (2019). Depression. Retrieved from https://www.merckmanuals.com/home/mental-health-disorders/mood-disorders/depression?query=depression
Jacka, F. N., O’Neil, A., Opie, R., Itsiopoulos, C., Cotton, S., Mohebbi, M., … Berk, M. (2017). A randomised controlled trial of dietary improvement for adults with major depression (the “SMILES” trial). BMC Medicine, 15, 1–13. https://doi-org.lopesalum.idm.oclc.org/10.1186/s12916-017-0791-y
Lai, J. S., Hiles, S., Bisquera, A., Hure, A. J., McEvoy, M., & Attia, J. (2014). A systematic review and meta-analysis of dietary patterns and depression in community-dwelling adults, The American Journal of Clinical Nutrition, 99(1), 181–197, https://doi.org/10.3945/ajcn.113.069880
National Institute of Mental Health. (2017). Any anxiety disorder. Retrieved from https://www.nimh.nih.gov/health/statistics/any-anxiety-disorder.shtml
National Institute of Mental Health. (2019). Major depression. Retrieved from https://www.merckmanuals.com/home/mental-health-disorders/mood-disorders/depression?query=depression
O’Neil, A., Quirk, S. E., Housden, S., Brennan, S. L., Williams, L. J., Pasco, J. A., … Jacka, F. N. (2014). Relationship between diet and mental health in children and adolescents: a systematic review. American journal of public health, 104(10), e31–e42. doi:10.2105/AJPH.2014.302110
Psaltopoulou, T., Sergentanis, T.N., Panagiotakos, D.B., Sergentanis, I.N., Kosti, R., & Scarmeas, N. (2013). Mediterranean diet, stroke, cognitive impairment, and depression: A meta-analysis. Annals of Neurology, 74(4), 580-591. doi: 10.1002/ana.23944