Dietary interventions show mixed results in treating perinatal depression and anxiety

By Dr. Liji Thomas, MDApr 4 2023Reviewed by Danielle Ellis, B.Sc.

Depression and anxiety are frequently treated with diet changes among women during pregnancy or postpartum. Not much is known, however, about the effectiveness of such interventions. A new research paper reports the findings of a systematic review aimed at identifying the benefits of such dietary modifications in these situations.

Study: Dietary interventions for perinatal depression and anxiety: a systematic review and meta-analysis of randomized controlled trials. Image Credit: fizkes / Shutterstock

Introduction

The perinatal period, stretching from conception to one year following childbirth, is a vulnerable time for expectant and new mothers. Up to a fifth of them experience depression or anxiety at this time, affecting their quality of life and health and that of their babies and families. Sadly, only about a tenth of these patients are treated with evidence-based protocols, even though the ill effects of depression are well-known.

Psychotherapy is supposed to be among the better interventions but faces a constant problem due to low numbers of available therapists, high costs, low coverage, and funding. In addition, psychotropic medications are often avoided due to the perceived risk of teratogenicity or fetal adverse effects.

Many women think that dietary interventions are safe and trace psychological disturbances to nutritional abnormalities that can be corrected via dietary modifications. Supplements touted to improve depression or anxiety symptoms are perceived to be natural and are relatively accessible and cheap compared to prescription medications.

Over 80% of women report one or more dietary modifications during the latter months of pregnancy. The current review, published in The American Journal of Clinical Nutrition, examines the effectiveness of such interventions in treating perinatal depression or anxiety. The findings could help shape better guidelines for the clinical management of such women and identify the role of dietary interventions, whether as primary or adjunct therapies.

What did the study show?

The researchers used 28 articles on dietary interventions to treat perinatal depression with or without anxiety. These studies came from several countries, the most significant number being from Iran and the USA. While over half assessed the effects of supplementation with omega-3 and omega-6 fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), others dealt with elemental metals, probiotics, vitamins, and amino acids.

Independent analyses were conducted for each of the interventions and the timing of the intervention (pregnancy vs. postpartum). Since EPA and DHA have been shown, in earlier research, to act via different pathways and affect the organism differently, the impact of varying EPA: DHA ratios were also evaluated.

The investigators found that polyunsaturated fatty acids (PUFAs) did not mitigate the symptoms of perinatal depression significantly compared to controls.

This was the case whether the intervention occurred during pregnancy or postpartum. Secondly, the intervention had no significant impact on the risk of perinatal depression or anxiety at an EPA:DHA ratio of <1.5 or ≥1.5.

Some earlier reviews indicated a potential role for PUFAs in treating perinatal depression, but the current paper negated such an effect. This could be due to the heterogeneity between studies, with multiple interventions being used simultaneously per study, or several eligible studies being excluded from some reviews.

The present study examined 13 studies with low levels of heterogeneity but found no role for PUFAs. A lack of statistical power, or the use of different dosages or periods of administration of PUFAs, may account for the lack of impact of these supplements, as they may not take effect over short durations of treatment. Low levels of severe depression among the study participants could also reduce the overall impact of the supplements. 

Again, elemental iron, zinc, or magnesium supplements did not improve the symptoms of depression in pregnancy. However, iron could be useful in treating women with low iron levels.

Copper supplementation from week 17 onwards, at 1 g/day, reduced depressive symptoms. Vitamin D did show a small but significant improvement in symptoms of postpartum depression.

“Based on our results, 1000 to 3500 IU per day of vitamin D for 8 weeks to 6 months significantly reduced symptoms of postpartum depression.”

An earlier study found that 2800 IU or more of vitamin D per day for eight weeks or more had the highest success rate. Currently, clinicians recommend 2000 to 4000 IU of vitamin D per day during pregnancy and postpartum.

What are the implications?

This is the first systematic review to examine only randomized controlled trials (RCTs), intending to shape decisions on mental health care during the perinatal period. The scientists covered macro- and micro-nutrients, separately assessed their impact at different stages of pregnancy, and produced a narrative synthesis of interventions in studies not eligible for the meta-analysis.

Since vitamin D seems to be associated with a slight increase in mental health, there is a need to establish the correct dosage of vitamin D supplements in pregnancy and postpartum to avoid and detect overdosage.

At the same time, they recognize the limitations of the included studies, such as significant bias, lack of baseline and outcome data, and failure to use uniform validated cut-offs for depression and anxiety scores.

“Using the GRADE approach, we have evaluated our quality of evidence to be moderate. Thus, our assessment of the existing evidence for dietary interventions for perinatal anxiety and/or depression can provide clinically relevant guidance for expectant and new mothers, as well as clinicians and researchers.”

Recognizing these limitations of a meta-analytic approach, the researchers recommend a network meta-analysis to better understand how and which non-pharmacological measures are of help in this condition. In addition, the standardization of treatment protocols and duration of treatment and follow-up is essential to compare the effectiveness of various interventions.

The effect of comprehensive dietary interventions remains to be examined. Overall, however, “The role of these interventions as monotherapy or as augmentation agents for other treatments (e.g., antidepressants, psychotherapy) is still not clear.”