In a new study published this month in the British Journal of Obstetrics and Gynaecology, Chinese researchers examined how timing of vitamin D measurement related to postpartum depression.
Postpartum depression (PPD) is one of the most common psychiatric conditions women develop after childbirth and is also a major cause of maternal mortality worldwide. While incidence has been reported to be as low as 0% of women in Singapore and as high as 56% of women in Brazil, typical estimates of PPD range between 10% and 40%. Symptoms usually begin within three months after childbirth.
Globally, the four main contributors to PPD are socio-economic status, demography, family history, and maternal and social support.
While several previous studies have linked low vitamin D levels with PPD, they have mainly evaluated the effects of vitamin D status during pregnancy and have not yet looked at Chinese populations.
There are a few lines of evidence to suggest a role for vitamin D in depression. First, the brain has numerous vitamin D receptors and vitamin D deficiency may interfere with normal cognitive functioning. Vitamin D has been shown to play a role in brain development and in the production of norepinephrine and dopamine, two hormones linked to depression.
This study was designed to see if symptoms of PPD are more common in Chinese women who have low vitamin D immediately following giving birth.
Women delivering full-term babies at the Peking Union Medical College Hospital were invited to take part in the study. Blood samples were drawn 24-48 hours after delivery to determine their 25(OH)D levels.
Women were excluded from participating in the study if they were under psychiatric care during pregnancy, had a stillborn infant, were giving birth to more than one baby, or had an infant that was immediately admitted to intensive care after birth. Two hundred and thirteen women with a median age of 31 years completed the study.
Three months later the women returned to complete the Chinese version of the Edinburgh Postnatal Depression Scale (EPDS), a screening tool used to identify if new mothers are suffering from depression. They were also interviewed to find out if they were breastfeeding, experiencing any health problems, and to report other lifestyle and socio-demographic factors that may confound the results.
The researchers wanted to know if vitamin D status within 24-48 hours after giving birth was significantly related to PPD and if this relationship persisted after adjusting for confounding factors.
Here’s what the researchers found:
- Overall, 26 of the women were identified as having PPD.
- There was a significant negative relationship between vitamin D status and EPDS score (P < .0001). This remained significant after adjusting for factors such as age, stressful life events, education, partner support, and previous psychiatric care (P = .006).
- Women with 25(OH)D levels above 14.3 ng/mL were the least likely to suffer from PPD (p < .0001)
- Women with 25(OH)D levels below 8.3 ng/mL were the most likely to suffer PPD (P < .0001)
- After adjusting for the above factors, the analysis showed that women with higher vitamin D status had a significant 19% reduced risk of PPD (P < .0001).
The authors identified some limitations of the study:
- They did not measure 25(OH)D levels during pregnancy to see if the women were low during pregnancy too and not just immediately after delivery.
- Even though women were excluded from the study if they had been receiving psychiatric care, some of the women who participated could have had undiagnosed mental health conditions.
- The PPD diagnosis process did not include a structured clinical interview.
Vitamin D supplementation is a low-cost and safe intervention and all pregnant women should be screened for vitamin D deficiency to prevent the severe deficiency states seen in the women in this study.