Doing more than an hour of moderate intensity exercise each week may reduce the severity of “baby blues” and almost halve the risk of new mothers developing major clinical depression, the largest analysis of evidence suggests.

However, researchers behind the study acknowledged that finding the time amid so many new responsibilities and challenges would not be easy, and recovery from childbirth should be prioritised.

New mothers could restart exercise with “gentle” walks, which they could do with their babies, and then increase to “moderate” activity when they were ready, they added.

This moderate physical activity could include brisk walking, water aerobics, stationary cycling or resistance training, according to the team of academics in Canada.

Maternal depression and anxiety are relatively common after giving birth and associated with reduced self-care and compromised infant caregiving and bonding, which could in turn affect the child’s cognitive, emotional and social development, the researchers said.

Conventional treatments for depression and anxiety in the first weeks and months after giving birth mostly involve drugs and counselling, which are often associated with, respectively, side-effects and poor adherence, and lack of timely access and expense.

Research has previously shown that physical activity is an effective treatment for depression and anxiety in general. But until now it has not been known whether it could reduce the severity of the baby blues in the first few weeks after giving birth or lower the risk of major postpartum depression several months later.

In the analysis, published in the British Journal of Sports Medicine, the researchers looked at 35 studies involving more than 4,000 women from 14 different countries. The team pooled data from available evidence on the impact of exercise after childbirth.

The risk of developing major postpartum depression was reduced by 45% among those who engaged in exercise compared with those who did not. And exercise was associated with less severe symptoms of depression and anxiety after giving birth.

Starting exercise before 12 weeks after birth was linked to a greater reduction in depressive symptoms than starting it later. And the greater the exercise volume the greater the reduction in the severity of symptoms, the research found.

To reap the benefits of exercise, women should try to engage in at least 80 minutes of moderate intensity exercise each week, the academics said. Ideally they should try to be active on at least four days of the week, they added.

The lead author, Prof Margie Davenport, from the University of Alberta, said light exercise in the early weeks after birth, such as gentle walking, could really help.

“Once [the mother] has recovered from labour and delivery, going for short gentle walks is encouraged. Walking is a great way to get exercise, and it’s something you can do with your baby,” she said.

“As she is ready to begin more vigorous exercise, we recommend a gradual but progressive fashion.

“It’s important that attention is paid to symptoms such as poor recovery after exercise which may mean that exercise is progressing too quickly. Those who experience urinary incontinence are recommended to speak to a pelvic floor physiotherapist for assessment and treatment.

“Everyone’s ideal starting time will be different, balancing the need to recover and heal from childbirth with readiness to begin being physically active to derive both physical and mental health benefits.”