The Leader of the Commons and Lord President of the Council said: “I still remember holding that tiny baby in my arms and feeling completely helpless.
“I have this abiding memory of snow outside and filthy windows and being in tears at the prospect of having to find a window cleaner. You know, the prospect of cleaning the windows myself was utterly beyond me.”
Mrs Leadsom spoke at an event organised by the mental health research charity MQ, on the House of Commons Terrace.
The Cabinet Minister said: “Mental health is a cause very close to my own heart and it affected me very personally. When my eldest son [Freddie] was born in 1995 I suffered postnatal depression.
“You just can’t imagine until you have suffered poor mental health just how awful it makes you feel and how helpless. It’s a very real, incredibly debilitating experience for far too many women when they’ve had a child.”
She overcame the illness with the help of her “amazing husband” of 25 years, Ben Leadsom, her family and “by going back to work” as a Barclays senior executive.
She went on to have another son, Harry, and a daughter, Charlotte. Pointing out that men can also suffer postnatal depression, Mrs Leadsom said: “But there are many others who take a very long time to recover from postnatal depression or who never get over it at all. Far too many cases of a mother committing suicide and taking their babies with them.”
The 54-year-old said the consequences can be “ever more severe” for babies and stressed the importance of early intervention.
“I would argue that the first 1,001 days of a baby’s life are critical and that’s the period from conception to the age of two.
“The peak period for the growth and development of the social part of a baby’s brain is six to 18 months and that growth is largely stimulated by the loving relationship with his or her primary caregiver.
“So a baby who is hugged, fed, attended to, smiled at and engaged with literally learns that the world is a good place. Such babies are likely to grow up with sound emotional health that leaves them far better able to deal with life’s ups and downs.
“But where a baby doesn’t have a secure bond with their primary carer, or worse still where there’s neglect or abuse and that’s the norm for them, that baby’s social brain will not develop in a way that provides lifelong emotional health.
“The outcomes for those with insecure or disorganised attachment can range very broadly but some of the outcomes for them are struggling to be happy, to make friends, to hold down a job, or at the most extreme end – criminality, substance misuse, self harming and many of the worst outcomes in our society.”
Mrs Leadsom founded and is patron of a charity called Parent Infant Partnership UK, which supports struggling families in the ante and postnatal periods.
“Mental illness is not only often under-reported but goes untreated. We have to prevent and treat the whole spectrum of mental health issues faced by society,” she said.
The UK government is the only one to have placed parity of esteem for mental and physical health on a legal footing and she said an additional £1billion a year will be spent on mental health until 2021, which would go towards employing an extra 1,000 practitioners.
Mrs Leadsom apologised to Theresa May after she was accused of suggesting that having three children made her a better choice to be prime minister.