Access to green space linked to reduced risk of postnatal depression in new mothers

Postnatal depression – depression or low mood experienced after the birth of a child – is a relatively common issue for new parents. The NHS estimates that 1 in 10 women experience postnatal depression, though new fathers can also experience mental health difficulties during this period.

There are a number of risk factors related to postnatal depression, including a previous history of poor mental health, poor relationships, and a lack of support. And a new study in The Lancet Regional Health - Americas looks at another risk factor: exposure to nature. The team finds that living in proximity to green spaces is associated with a decreased risk of postnatal depression.

The study focused on an area in Southern California in the US which has a diverse population. The team looked at 415,020 pregnancies in this region between 2008 and 2018; those who had multiple births, who gave birth to stillborn babies, and who lived in rural areas were excluded from the analysis. The researchers extracted various data from the mothers' electronic health records, including details of how much they exercised during their pregnancy, and whether they had been diagnosed with postnatal depression and prescribed medication.

The researchers used various methods to assess the amount of green space near each mother's home. This included analysing street view images within a 5-10 minute walk of the house, with total green space being defined as the proportion of space taken up by trees, low-lying vegetation, and grass. They also looked at satellite images of green space and tree canopy cover, and looked at participants' proximity to the nearest park.

Reflecting existing data, around 10% of participants exhibited symptoms of postnatal depression. However, mothers with more total green space near their home, as assessed by street view data, were less likely to experience postnatal depression. Higher tree coverage was also associated with a decreased risk of postnatal depression.

The team found that this was partly due to the fact that women living around more green space tended to get more exercise during pregnancy. In turn, more exercise was related to a reduced risk of postnatal depression. However, physical exercise could only partly explain the link. The researchers suggest that green space might also facilitate social contact and neighbourhood safety, both important contributors to mental health.

The researchers also identified certain demographic factors that were related to the amount of green space around participants' houses. Older mothers, mothers with higher education, mothers who live in high-income neighbourhoods, and white mothers were more likely to live near green spaces and near trees and low-lying vegetation. The relationship between green space and risk for postnatal depression still held after controlling for these demographic factors, so it wasn't simply that more privileged participants were protected from postnatal depression in other ways. However, these results do suggest that poorer and less-educated mothers, or those from ethnic minorities, may have less access to green space, and therefore to the apparent protective effect of living around nature.

The study could have implications for urban planners: developing spaces for everybody to experience nature, especially those in deprived areas, could help with mental health in new mothers as well as others.