Women who gave birth amid the UK's first coronavirus lockdown were over twice as likely to endure postnatal depression as those who had children pre-pandemic, research suggests.
Early in the outbreak, experts warned it could have a "profound" and "pervasive" impact on people's mental health for some time.
To better understand how new mothers have been affected, scientists from University College London sent a survey to 162 women in May and June 2020.
Results reveal almost half (47.5%) of those with babies under six months old met the diagnostic criteria for postnatal depression, generally defined as a new mother feeling persistently sad, withdrawn and even struggling to bond with her baby.
This is more than double the 23% of European mothers who experienced the condition pre-pandemic, according to the scientists.
The affected women reported feeling isolated, stressed and anxious about their child's development amid the "stay at home" restriction.
"Caring for a new baby is challenging," said study author Dr Sarah Myers. "All new mothers suffer some level of mental, physical and emotional exhaustion.
"Low social support is one of the key risk factors for developing postnatal depression.
"Social distancing measures during lockdown created so many barriers to having practical help and meaningful support from others in the weeks and months after their baby's arrival, leading many new mothers to feel totally overwhelmed."
Writing in the journal Frontiers In Psychology, the scientists reported that 23% of new mothers generally experience postnatal depression across Europe.
According to the NHS, however, around one in 10 women develop the condition within a year of giving birth, with fathers and partners often also affected.
Watch: Help for postnatal depression
The 162 mothers, who all lived in London, had their wellbeing assessed via the Edinburgh Postnatal Depression Scale.
Among those who met the definition for the mental health disorder, many reported feeling inadequate, guilty and unusually exhausted.
Some "grieved" for the opportunities lost to them and their babies, with lockdown limiting playgroups and family get togethers.
Women whose partners could not help with parenting and household chores, particularly when forced to carry out home schooling, were worst affected.
"New mothers with more than one child were hardest hit, left to deal with newborns on top of multiple demands like home schooling," said co-author Dr Emily Emmott.
"First-time mothers often felt cheated out of precious time spent together with their babies and family or friends, making coming to terms with the change of identity and isolation that new mothers often feel even harder."
The more contact the women maintained with their loved ones, either remotely or face-to-face, the fewer depression symptoms they endured.
Perhaps surprisingly, the women who had some face-to-face contact with family members were more likely to develop postnatal depression than those who saw less of their relatives.
The scientists have put this down to families potentially breaking lockdown in order to support a struggling mother.
Many of the affected women felt the restrictions led to a "burden of constant mothering", with virtual support being inadequate.
With loved ones less able to pick up on a mother's depression, some of the women felt they had to actively ask for help, which was stressful in itself.
One of the mothers surveyed said: "I think lockdown has made me feel like I'm not a person in my own right any more.
"Not having anyone to hold him or to help out a bit makes me feel it's all me and it's a lot of pressure, which I can resent. I feel like I don’t have any time to rest."
Another added: "It has definitely made me more anxious – 'am I doing enough for my baby, is she okay, is she healthy and happy, should I be doing more, do people think I’m a good mother?'
"Much of this is because it's hard to communicate online."
Watch: Women more likely to be depressed in third lockdown
"It really does take a village to raise a child, especially in a crisis when everyone is dealing with increased demands, stresses and significant life events," said Dr Myers.
"Our survey shows lockdowns leave new mothers more vulnerable to postnatal depression and digital solutions might help, but they are not the answer.
"Policymakers must take this into account as we continue to deal with COVID-19 [the disease caused by the coronavirus], for the sake of mums, babies and whole families."
In more positive news, some of the women enjoyed the extra family time, as social plans had to be called off. Others also benefited from their partners working from home.
"Where partners were at home more because of lockdown, and able to share the relentless tasks and household chores or take care of existing children, new mums felt the benefits," said Dr Emmott.
"Some reported it helped everyone develop closer relationships and the family benefited overall from spending this time together.
"This should also be food for thought when we look at support for parents with new babies, not just in a pandemic."
The NHS recommends people with postnatal depression speak to their GP or health visitor.
Therapy and antidepressants can be effective. Patients are also advised to open up to loved ones, make time for things they enjoy, rest as much as possible, eat well and exercise regularly.