“I don’t believe there’s anything wrong with you.”

The psychiatrist’s words pierced like a bullet. Months of suppressed grief became fat, heaving sobs and one defeated plea, “why are you doing this to me?”, before I ran out and collapsed at my husband’s feet. We’d been cut loose, left alone to career through my delirium. What could we do now?

At the height of my illness, I remember the smell of the bubble bath, how its sweetness crawled up my nostrils as I sat in the 10 inches of water I’d been permitted: jasmine, ylang ylang, shea butter. My mother had been summoned, and I’d been placed there for safekeeping while the phone calls were made, in the hastily mummy-proofed room, where any sharp object had been quickly bagged and removed. The baby’s cries came up through the floorboards, as did the quieter, heavy sobs of a grown man, my husband. I was a prisoner, with a thunder in my chest and a voice in my head – once a solitary whisper, which had multiplied and was now cacophonous. Arguing. Sibilant. Indecipherable. Perfectly still, I lay flecked with goosebumps.

In days, I’d gone from being a happy mother, high on my new arrival, to a husk, torpid and terrified of my own breath passing my lips. I was suffering from postpartum psychosis: postnatal depression’s bigger, uglier brother, which occurs in about one in every 1,000 women. It’s a severe mental illness that robs you of reason and your grasp on reality, all too often with tragic consequences.

Two years previously, I’d endured it after the birth of twins, for close to 18 months: the obsessive thoughts, compulsions and detachment, the vigilant night watch that robbed me of sleep, and the unshakeable belief that my babies were about to die, that my blood was clotting in my veins and would kill me any minute. My memories of their early years are stained with fear and dread. I’d approached my GP about my mental health during my subsequent pregnancy, but they went little further than a quick screening and assurances that I’d be fine because I was “well now”.

A few hours before that bath, I’d climbed out of bed to feed my new son. A baby, allergic to milk, including my own, and battling reflux, who seemed to exist only to cry and vomit incessantly. Sleep hadn’t found me since the previous feed. Tiredness sat heavy in my bones, and my mind had glitched, with one obsessive phrase on a loop: “Give him back.” He weighed nothing, but lifting the 6lbs of struggling confusion took every ounce of effort I could muster.

I prepared the special formula, fed him, traced his tiny face with my fingers, inhaled his cotton-wool hair, kissed him between the eyes, and settled him to sleep. I’d tried to sing, but only broken croaks escaped as the salt water dripped on to his blankets.

I left the house in the middle of the night, barefoot and in pyjamas, intent on ending my life. Living was beyond me. I didn’t recognise my mind. My reality had been inverted, and I was trapped with a hostile imposter filling my head with constant noise, images and impulses.

The mother and baby unit I ended up in was one of only two in Scotland, and found space for me among the handful of beds. Decorated in inoffensive pastels, there were home-like touches for the oblivious babies and their mums, who floated around like ghosts in baggy shirts with unwashed hair. Despite the best efforts of the staff, sadness clung to the walls as much as it did to us. My son smiled for the first time on the playmat as I lay prostrate on a sofa staring through the television, wishing for sleep and to not wake up.

There were interviews and helping hands, then, a mix-up. The staff were concerned I was feigning illness for sympathy, and making my baby ill for attention. We were abruptly discharged, and bounced to the clinical psychiatrist at another hospital. The assessment was that, despite previous serious postnatal depression, I was a malingerer taking everyone in. I was accused of manipulating hormone results through expressing the milk my baby couldn’t have, in order to gain treatment. Eighteen months of paediatric gastroenterology and endocrinological sleuthing would finally lay this accusation to rest. In the meantime, we tried to rebuild our lives, but couldn’t. Without support, we had no idea how to put the pieces of a normal life back together. I watched the people close to me melt away.

When it comes to physical symptoms you can see them, test them and treat them. But if you’re a new mother, paralysed by fear and suffocated by despair, you had better convince the doctors. Asking for help isn’t always enough. Psychosis doesn’t live up to its Hollywood image; instead it’s often a silent erosion of your own existence, which makes it hard to spot. When delusions and reality blend so seamlessly, you don’t have the self-awareness to shout out. The voices are your reality. And the toxic thoughts. You become caged inside yourself so abruptly that you simply cannot find the fortitude to reach out.

When one in five women suffer from mental illness during and after pregnancy, our screening has to get a lot better than overworked health visitors and midwives handing out questionnaires. Those at risk must be noticed and supported effectively during pregnancy, and after birth. There are just 20 specialist mother and baby units in the UK, each with only a few beds and many mothers needing long-term help. That leaves thousands of women scrambling in the dark, and struggling to cope with hands-off, outpatient treatment.

Acute mental illness is an emergency that needs responsive care. When all eyes are on a beautiful baby, too often we forget to look at the mother.

• In the UK the Samaritans helpline number is 08457 909090

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