TODAY should be a happy one. It's Dorothy and Walter Schwarz's golden wedding. But there's no air of celebration. As Dorothy explains quietly, such anniversaries don't have the same significant once one of your children has gone in tragic circumstances.

Last week we told the story of Zoë Schwarz, who committed suicide at the age of 27 while suffering from bipolar depression. Today, Steven Russell asks Dorothy Schwarz why she wanted to write a book about her daughter's illness

TODAY should be a happy one. It's Dorothy and Walter Schwarz's golden wedding. But there's no air of celebration. The family never much was one for over-hyping occasions like birthdays; and, as Dorothy explains quietly, such anniversaries don't have the same significant once one of your children has gone in tragic circumstances.

One of the saddest features of her book, Behind A Glass Wall, is the Schwarzes' sense of guilt in not recognising the reality of the situation. Sometimes they felt Zoë's behaviour was a conscious act, rather than the symptom of an insidious disease; at other times they trawled the past to see if the trigger was something they did or did not do.

But bipolar depression is in all likelihood a neurobiological brain disease affecting one in 100 people, and not something caused by separation from a childhood nanny, the sale of a slightly troublesome horse, or the death of a loved cat.

A psychiatrist told the family that while psychiatry does help a lot of people, it is still terribly imprecise.

If the professionals find it less than black and white, what hope for bewildered relatives ill-equipped for a battle with an intangible illness pulling their loved one into a black hole?

In her book, Dorothy talks of one incident that's particularly hard to bear. They'd had Zoë's old and neglected car repaired in the hope she'd respond to the extra independence it offered. It was the vehicle she drove to Marks Tey railway station before killing herself.

Today, having had a bit of time in which to reflect, does Dorothy accept she was too hard on herself?

“Yes,” he replies, slowly, “but I was brought up in a Judeo-Christian tradition of guilt. I think there's a basic fact of nature: we aren't programmed to survive our children. 'I'm her mother; I should have looked after her better. I let her walk off to her death.' But then I had no idea she would kill herself. So yes, I am hard on myself; but if it makes other people a bit more cautious . . .”

Does Dorothy now believe that Zoë's condition was almost certainly down to internal chemical dysfunction/misalignment - whatever one wants to call it?

“Totally think that. We all have problems. We all grow up with awful things having happened to us. We all get disappointed. We don't actually all kill ourselves. I think to kill yourself when you're someone like Zoë, who had so much joy in her life, who was loved, I think your brain has to go wrong.”

She and Walter had no knowledge then of bipolar depression, so alarm bells did not ring loud or long enough when things happened.

“Even in her last months, it didn't cross my mind she was going to kill herself. But looking back on it, 'Of course . . .' She had all the symptoms: she'd got to talking in a hollow voice, which is one of the pre-symptoms for suicide attempts. The weekend that she died, she got much more cheerful, and I sent everybody emails: 'Oh, Zoë's getting better.' But she'd obviously decided, and so was calm. The corner had been turned, but to the left and not the right, and that's something I have to live with for the rest of my life.”

Dorothy explains: “There were two mistakes that we made: one is believing that people who talk about suicide never do it, which is not true, and the other is thinking that once you've made one attempt you're inoculated. That's what Zoë believed all through her 20s: 'I've been to the bottom. I'm strong. I won't go to the bottom again.' But that's not the case. Statistics show that people who have made serious attempts and failed will very often do it again.”

The Schwarzes have never harshly criticised their daughter's care, but do wonder why they were never informed Zoë was regularly talking about suicide during her psychiatric sessions - though she did also say she would never do it.

Medical staff, Dorothy accepts, did their best, “but somebody should have said to us 'Well, she does talk about suicide. She says she's not going to do it, but she talks about it”.

Had Dorothy known this, “The morning I went shopping and left her at home, I would have stayed with her.”

There was a plan for Zoë to go into hospital and start a course of lithium treatment, but previous experiences of hospital had left a deep-rooted fear.

“One of the errors we made was to let her go into hospital in the middle of her depression. She saw a lot of people who were in a contained state on drugs, shuffling around, and she said to me 'I don't want to be like that.' I think it totally terrified her and she wouldn't stay there more than four days.”

Dorothy wrote the book because she felt Zoë wanted her collection of letters, diaries and other writings to be read. “Her life was so short, I wanted there to be a record of it, and for people to know that she'd suffered and she'd tried.

“Another motive, a very strong one, was that I felt one of the things that killed her was the stigma of mental illness. I said to her, lots of times, 'Well, you know, you've got a diagnosis. Think of Sylvia Plath and Spike Milligan - people with manic depression. Kurt Cobain was another.' I wanted to try to lessen that stigma.”

Not everyone thought the book a good idea. Dorothy admits her other children generally don't like what they see as dirty linen being washed in public. But their mum wanted to emphasise that Zoë's dysfunction, her manic and erratic behaviour with spending, drugs and sex, was caused by her illness.

The newspaper article the couple wrote in 2002 ends with the wish: “For ourselves, we conclude that parents, siblings and friends of bipolars need, before the crisis overwhelms everyone, to see it coming and find a way to persuade the patient to seek treatment instead of smoking pot from breakfast to bedtime.”

(Last week's article can be found online in our features section at www.eadt.co.uk - headlined 'I love you but can't live like this.')

Behind A Glass Wall is published by Chipmunkapublishing of Brentwood. (www.chipmunkapublishing.com) at £12. ISBN 1-904697-20-8

THE BBC is this autumn expected to feature Zoë Schwarz's story in a documentary on bipolar depression.

A crew spent a day filming at the family home near Colchester, with presenter Stephen Fry interviewing the couple, and also shot footage at the London Book Fair.

Dorothy says it has proved one of the positives to flow from the tragedy.

Stephen Fry has himself suffered with bipolar. “He knew about Zoë both because he'd been briefed and because he's been there too.”

There were amusing moments, too.

“In a break - I think the crew was filming videos we've got of Zoë - Stephen went into the end room and I just followed him. I found him reading a Goethe poem in German.

“He was standing by the piano and my little female parrot was standing in front of him, totally entranced. She literally fell in love with him reading this German poetry.

“I said to Stephen 'Do you know what she's doing? She's propositioning you!' Wings fluttering, she was literally besotted. He's one of the most devastating men I've ever met in my life; he had intelligence like a rapier. And a lot of humanity. Although he was the star, he didn't pull rank, and took immense trouble with detail.

“Seeing Zoë's life given to people like that was some sort of closure to me - particularly that they understood. To have somebody who had conquered that illness and totally understood it was a great feeling.

“We were at the London Book Fair and people were 'terrorising' Stephen, and he leant across and said 'Zoë would have enjoyed this, wouldn't she?' And she would have. She had a lot of charisma and was a star.”

At one side of the Schwarzes' garden is a long aviary. Dorothy now has 18 parrots and says caring for them has been a help in the six years since losing her daughter.

The first parrot arrived in the spring of the year Zoë died and started life as Arthur - changed to Artha when it was realised he was in fact a she. There's a video of Zoë holding Artha, whom she loved.

Dorothy insists she doesn't want to be known as a “suicide mum”, forever talking about the experience.

She's busy writing about parrots and is interested in conservation. “And what I would like to go on doing for the next 10 years is seeing my grandchildren once a week” - there are five altogether - “because they are the joy of our lives.”

DOROTHY'S book raises some questions about treatment, which the North Essex Mental Health Partnership NHS Trust agreed to answer.

The trust said: “The organisation has in recent years achieved national recognition for its approach to cases when people who have used our services commit suicide . . . We want to do everything we can to reduce the possibility of similar situations occurring again.

“The nature of mental illness means that it can be very difficult to predict someone's actions. A full investigation is always conducted when an individual we are supporting takes their own life.”

Why aren't families told a patient has spoken of suicide (albeit that they might also have said they would never do it)?

“Legally, professionals are bound by patient confidentiality. By law we are required to respect the wishes of patients and cannot share information with relatives unless consent has been given.

“Staff try to work in partnership with the individual's family and carers to inform them of mental health issues. Patients are continually encouraged to discuss how they feel with their family and carers so they can be aware of the issue and offer support. However, it is ultimately the decision of the patient if they wish to disclose such information.”

What about the issue of medical staff holidays?

“Before consultants go on holiday a consultant must hand over to an appropriate colleague. It is difficult to foresee what may happen when the consultant is away and it is not always possible to plan the handover well in advance. However, especially with complex cases, the patient is often consulted with to ensure a smooth transition across to the interim clinician.”

Although The Lakes's bright rooms and pleasant garden were a vast improvement on the Victorian institution it replaced, her mother says the atmosphere of lethargic hopelessness only increased Zoë's depression.

The trust said: “Often, a patient's perception of a hospital environment varies throughout their care and treatment, depending on how well they are and who they are interacting with.

“Following work with the patient and public involvement forum, feedback from our users and trust-wide initiatives, we have made a number of improvements.

“One of our most important developments is the improved support we offer individuals at home. We now have dedicated teams to provide intensive support when people are experiencing a mental health crisis.

“The teams offer frequent home visits and assessment to help prevent an individual deteriorating to the point when hospital admission is the only option for care. The programme means that people receive care in the comfort of their own setting. Evidence suggests that this is a good way to support people, and admissions to psychiatric wards have dropped significantly since the initiative was introduced.”

It added: “We have worked with patients to develop a therapeutic programme. This includes dedicated time with nurses, art therapy and psychotherapy. The aim of this is to encourage people to interact with other patients and health professionals.”