Theroux visits two specialist psychiatric units in the UK that treat mothers suffering from depression, anxiety and psychosis.
"I thought it would be powerful to explore the idea of what is supposed to be this magical and amazing time of creating a new life, and those first weeks and months of caring for that new person, when it’s all overlaid with deeply distressing mental illness. It seemed to me both very sad but also potentially life-affirming, in the sense that we’d hope to share the reality of the condition to create more awareness of it and follow people as they recover from it,'' he said.
The film follows the new parents home after treatments to see how they move on.
"There’s something wonderful and warm about seeing all the babies. I have three children, and my youngest is four, so it’s not long ago that he was a baby, and it bought back a lot of happy memories for me,'' he said.
"I’d like people to take on board that there are forms of mental illness that, in many ways, aren’t massively different from the complicated feelings that new parents have, such as struggling with having a baby, struggling with your own responses, feeling guilty when you feel they’re not the right responses, or having anxiety about not feeling enough love. It’s not easily explained, and even the psychiatrists and patients themselves struggle to put into words what it is they’re feeling and why.''
There was one topic that Theroux took on, that even he, admitted was incredibly challenging. The case of mothers harming their own babies.
"I think there’s a lot of misunderstanding around the subject. One of the things we tried to get our heads around while making the film, was that even though we hear about mums who get intrusive thoughts of harming their babies, it that doesn’t mean that they’re actually going to do it. Sometimes the mind plays tricks on you or torments itself. It’s just part of a bigger picture of mums grappling with a mindset that’s not doing exactly what it’s supposed to, and throwing up ghoulish examples to itself.''
The film ultimately is a testament to mothers and their babies.
“The women we featured in this film took a huge leap of faith in opening up and speaking to me. They bared a lot of their souls and risked the judgement of less understanding elements of society. Their bravery and candour is awe-inspiring, and it was a privilege to be invited into their families during a most vulnerable period in their lives.''
Mothers On The Edge will air on BBC2 in May 2019.