Postnatal depression rates make up more than 20% of new mothers in the US, UK and Australia.

Depression affects a woman’s health, her ability to bond with her baby, and the entire family unit.

Reducing rates of postnatal depression (PND) is important for society as a whole.

Mental health in general is a vital public health topic.

It’s difficult to pinpoint the causes and best treatments for depression.

But it’s important we continue to research ways to reduce the rates of depression.

For women with a history of postnatal depression, welcoming a new baby can bring on worries about PND.

For women with no history of postnatal depression, experiencing PND can come as a big shock.

It can even take a while for these women to seek treatment.

Many women are unaware what they’re feeling is more than typical adjustment to motherhood.

Postnatal Depression Rates Linked To Daylight Exposure

Researchers at the University of California San Francisco looked at the link between exposure to daylight during the last trimester of pregnancy and the risk of developing PND.

Research has shown an association between less daylight and low vitamin D and the risk of depression in general.

Until this study, there hadn’t been research focusing on daylight and the rate of PND.

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Less Exposure To Daylight Associated With An Increased Risk Of Postnatal Depression

Routine screening for vitamin D in healthy adults isn’t recommended by international clinical practice guidelines.

Until recently, vitamin D screening wasn’t routine for pregnant women.

However, routine screening of populations at risk for vitamin D deficiencies is now becoming standard practice. This includes screening of pregnant and lactating women.

These days, most people spend the bulk of their time indoors.

Vitamin D deficiency is therefore more common.

In recent decades, research has found associations between low vitamin D and depression.

Researcher Deepika Goyal and her colleagues at the University of California San Francisco looked specifically at exposure to natural daylight and the risk of PND.

Goyal looked at available data for 293 first time mothers from the US state of California.

The general risk of depression among these women was 30%.

However, the rate of depression varied, based on the amount of natural daylight exposure they had during their final trimester.

Women with the lowest risk of depression (26%) had their final trimester during the season with the most daylight.

Women with the highest risk of depression (35%) had their final trimester during the season with the least amount of daylight.

In the northern hemisphere, where this study took place, that coincides with the end of August through to early November.

Goyal summed up the research saying:

“Among first-time mothers, the length of day in the third trimester, specifically day lengths that are shortening compared to day lengths that are short, long or lengthening, were associated with concurrent depressive symptom severity”.

The rates aren’t massively different (9% difference in risk, based on this study).

But researchers found the severity of depressive symptoms was higher in women who had their last trimester during shorter days.

What Does This Research Mean?

Although this research is newer and more detailed, it confirms other associations we were already aware of.

Less exposure to sunlight and lower vitamin D levels are associated with a general increased risk of depression.

This study simply looked specifically at the links to PND.

Healthcare professionals could use this research to recommend that pregnant women:

Take a vitamin D supplement
Get as much natural sunlight exposure as possible (spend more time outdoors)
Consider light therapy.

For pregnant women, this research can help them make informed choices about lifestyle and supplements.

Planning a pregnancy around a birth month can be tricky.

It’s worth considering the timing of conception and birth if you have very high risk factors for PND.

Why Are Postnatal Depression Rates So High?

It’s quite sobering to read 30% of a group of women faced Postnatal Depression. That’s nearly 1 in 3.

Not all studies or groups show such high rates, but it’s clear the rate of depression among new mothers is too high.

There’s no one single cause or risk factor for PND.

However, in addition to this new study, other research has found many risk factors and correlations.

A history of depression is a big risk factor for PND.

Therefore it’s important women continue to work with their healthcare providers to manage any symptoms during and after pregnancy.

Our birth and parenting culture is also likely to play a role.

In many places, it’s common to have short prenatal visits.

This does not prepare women to know what to expect during pregnancy, birth and the postnatal period.

In the US, nearly 1 in 4 new mothers return to work within two weeks of giving birth.

Nearly 1 in 3 women are expected to parent, with little support at home, just a few days after a c-section.

You can read more about our culture’s role in PND in Why Depressed New Mothers Aren’t Crazy, But Society Is.

In relation to this study, society dictates many of us spend the bulk of our time indoors.

Often we spend six to eight hours or more each day at school or at work.

During the shorter days of the year, that means little to no time in natural sunlight.

Low levels of vitamin D are associated with depression and even with poor immune system function. Both of these are incredible challenges for new mothers.