Treating Depression: The Therapeutic Value of Dietary Changes
In the field of medical research, significant evidence suggests a connection between the quality of someone’s diet and their depressive symptoms. More specifically, diets with more fruits, vegetables, legumes, whole grains, and lean proteins (including fish) are associated with a reduced risk for depression, while diets with more sugary and processed foods are associated with a greater risk for depression.
Accordingly, researchers have started to wonder if dietary improvements could be used in therapy to help patients with psychiatric disorders. As a new research discipline, it requires randomized, controlled trials to explore this potential cause-and-effect relationship between diet and depressive symptoms. The study discussed here, called the Supporting the Modification of Lifestyle In Lowered Emotional States (SMILES) trial, is an attempt to help fill that gap.
Before delving into the trial, it’s helpful to review some of the tools the researchers used to assess participants’ depressive symptoms, since these tools are referred to throughout the article. To measure the severity of someone’s depression, clinicians use the Montgomery-Åsberg Depression Rating Scale (MADRS), which uses a point scale from 0 to 60 (with a score of 0 to 6 suggesting no symptoms). Another tool is the Hospital Anxiety and Depression Scale (HADS), which measures someone’s levels of anxiety and depression through questionnaires. Finally, the Clinical Global Impression-Improvement (CGI-I) 7-point scale is used to measure changes in symptoms.
The researchers hypothesized that an improved diet would reduce depressive symptoms more effectively than socializing would. The SMILES trial took place over 12 weeks and included 67 participants. To participate, each adult had to report that they had a poor diet (meaning a low intake of healthful foods and a high intake of unhealthful foods) and had experienced a major depressive episode. They were also required to have scored 18 or higher on the MADRS.
Each participant was randomly placed into one of two groups: dietary support or social support, with the latter being a control group. Over the 12-week study, the dietary support group received seven sessions of personalized dietary advice and counseling from a clinical dietician. The social support group followed the same schedule, but their sessions involved chatting about positive, engaging topics and playing games with the counselor.
Fifty-six participants completed the entire 12-week trial. Interestingly, more participants in the dietary support group stuck with the trial (93.9%) than those in the social support group (73.5%). The dietary group also showed greater improvements in their MADRS scores, with the group average decreasing from 26.1 to 14.8. In comparison, the social support group’s average MADRS score dropped from 24.7 to 20.5. Similar results were found upon reviewing the HADS scores in both depression (the dietary support group’s average fell from 10 to 5.3, and the social support group’s average dropped from 9.2 to 6.8) and anxiety (dietary: 12.1 to 8.4; social support: 11.2 to 9.5).
In addition, 32.3% of dietary support group participants and 8% of social support group participants received a MADRS score of 10, which is considered to be remission. Further, the CGI-I scale revealed that the dietary support group’s depressive symptoms had “much improved” on average, while the social support’s group symptoms “minimally improved.” As for diet, the dietary support group significantly increased their intake of healthful foods and decreased unhealthful foods, while the social support group showed no significant changes in diet. These effects persisted after controlling for prior diet, sex, education level, physical activity, and original BMI (body mass index).
What do all of these numbers and results mean? For one, this trial presents preliminary evidence that dietary changes may be an effective treatment for those with major depression. The scores across the scales overall show a significant decrease in depressive symptoms for these participants. And nearly all of the dietary support group participants saw the trial to its end, indicating the acceptability of these dietary changes. The authors also note that the participants’ weekly food costs went down by about $26 (AUS), suggesting that these dietary changes are affordable too.
Of course, this study is preliminary and more robust studies with larger sample sizes are needed. Regardless, the results of the SMILES trial support the notion that a person’s increased intake of fruits, vegetables, legumes, whole grains, and lean proteins — with a corresponding decrease in sugary and processed foods — can help treat clinical depression. The idea of food being medicine is becoming increasingly common, but trials like this one can help us develop more effective treatment plans in actual clinical settings. On a more general level, this study reminds us that healthful foods are not just good for our body, but good for our mind as well.