What new research tells us about dietary interventions for depression.
Despite decades of treatment attempts, depression continues to represent one of the biggest health problems in the United States. This debilitating condition affects millions of Americans, leading to widespread disability in both children and adults, and generating an economic burden in excess of $200 billion a year.
How significant is the issue? In 2017, depression was estimated to cause severe impairment in over 10 million American adults. Though the prevalence of depression is still painfully high in older populations, it is especially elevated in younger adults and adolescents, with 13% of the 18-25 year-old demographic suffering from this condition.
When it comes to treatment modalities for this devastating condition, there are still few evidence-based options available. Currently, providers primarily rely on two options: pharmaceutical interventions and psychotherapy. Unfortunately, even the best medications for depression suffer from relatively poor efficacy as well as high rates of side effects and withdrawal effects.
One glimmer of hope in depression research has been the new understanding that food could represent an additional treatment strategy for the condition. As I noted in a recent article, scientific literature has increasingly supported dietary modification as a therapeutic intervention for both treatment and prevention of depression.
This nascent field of research is still trying to determine the strength of the depression-diet connection. A 2018 review and meta-analysis on the subject concluded that a healthier diet was significantly associated with a lower risk of developing depressive symptoms, additionally finding that a less inflammatory diet was associated with a lower rate of depression when compared with a more inflammatory diet. The authors nonetheless caution that further studies, including randomized controlled trials, are needed.
Until recently, the only randomized controlled trial of dietary interventions for depressed adults was the 2017 “SMILES” study. In this trial, adults with depression were randomized to either receive nutritional counseling sessions or social support protocol for 12 weeks. At the end of the study period, researchers found those in the dietary intervention group had significantly lower symptoms of depression and were significantly more likely to have remission of their depression.
Then, in October of 2019, another randomized controlled trial was published in the journal PLOS ONE. Researchers in this study randomized young adults with depression symptoms and poor overall quality of diet to either three weeks of dietary intervention (which included a reducing refined carbohydrates, sugar, fatty/processed meats and soft drinks) or continuation of their standard diet. At the end of the study period, the students randomized to the dietary intervention reported significantly less depressive symptoms.
Despite promising results, it’s worth noting that both of these studies were rather small, each comprised of less than 100 participants. While the SMILES trial attempted to create an active control group (social support), the more recent PLOS ONE study simply left the control participants to their own devices. With this in mind, it’s easy to see why some experts feel we need more evidence before we can recommend diet as a therapeutic option for treating depression.
The idea of waiting for more data before action makes sense in many contexts. When the potential side effects from a treatment could be dangerous, or when the cost of an intervention is very high, we should take a step back before making any concrete recommendations to patients. When it comes to our current model of managing depression, however, it seems prudent to reflect on several facts.
First, while our current pharmaceutical therapies may provide a measurable benefit in depressive symptoms, this effect has been shown to be small, and comes with a considerable risk of side effects and withdrawal effects. Psychotherapeutic care for depression works, but may not be available to everyone, and is not effective for all comers. Despite massive numbers of Americans taking antidepressants (and a 400% increase in antidepressant prescriptions over the last few decades) depression rates do not appear to be improving, and may in fact be getting worse.
As such, the idea that we should skip a relatively low-cost, low-risk and study-backed treatment for this debilitating condition doesn’t make too much sense, especially given the clear additional benefits to healthier eating for so many other medical conditions. Certainly, dietary interventions won’t work for everyone, and may in fact be inappropriate for some. But at this stage, it seems completely reasonable to consider food part of a therapeutic plan for both prevention and treatment of depression.