The figure in the hospital bed was someone we barely recognised. Thin, unkempt and whey-faced, hair chopped off with kitchen scissors, I knew it was my daughter Lara, but something had changed her horribly.

We longed to throw our arms around her and cuddle her, but the antagonism in her eyes held me and my husband back.

This was something entirely new. Over the many, troubled years of our second eldest daughter’s life, my husband Shaun and I had seen many different Laras: the kind little girl who delighted everyone with her cheeky poems and limericks. The talented artist. The quicksilver violinist. The brilliant scholar with an acerbic wit.

And, latterly, the desperately-ill adolescent and young woman, trying to survive a world which often frightened and confused her.

But not this. Never this.

Anne Atkins has revealed her anguish over cannabis ruined her daughter's life

And then she let us have it, subjecting us to the most blistering few minutes of our lives, so painful I can hardly bear to repeat it: ‘I hate you. I’ve always hated you. I’ve hated you since I was 12, and I’ve never wanted you in my life. I don’t want you to speak to me for the next 20 years, to make up for my not having a voice as a child.’

I was shaking for a week after that dreadful morning in November 2013, and carried on crying every day for pretty much the next two years. What had transformed our lovely, 28-year-old, daughter into this bitter, spite-filled stranger?

Lara herself lays the blame unequivocally at the feet of cannabis, though she was never even an average user. She only ever allowed herself a puff or two a day, for medicinal purposes, and has used just 5 grams in total in her life.

But it was enough to make her high every day for nine months, and — tragically — enough to devastate her personality, perceptions, relationships, health and nearly her life.

So, when I hear of the liberal elite, led by Nick Clegg, calling for the legalisation of cannabis because ‘it’s not very harmful’ or ‘everyone’s doing it’, it makes me not just sad, but angry. The U.S. states of Colorado and Washington decriminalised cannabis four years ago. Not surprisingly, use is way up, including by minors — but so too is cannabis-related crime, homelessness, suicide, hospitalisation and alcoholism.

And the black market still thrives.

A cross-party group of MPs has called for an end to the ‘embarrassment’ that is our current drugs policy, and found that legalisation could bring in £1 billion in tax.

When Anne hears Nick Clegg calling for the legalisation of cannabis because ‘it’s not very harmful’ or ‘everyone’s doing it’, it makes her angry

Well I don’t care how embarrassing it is, or how much it nets. Cannabis is not the cuddly, harmless puff we pretend it is: it wrecks lives, as it wrecked our daughter Lara’s — incidentally, a very talented Cambridge graduate who could have been filling the country’s tax coffers in a much more wholesome way, but has never yet been able to work.

Nor is it true, as Conservative MP Peter Lilley said, that ‘currently cannabis can only be obtained from illegal gangs who also push hard drugs’.

Lara obtained hers from a family friend, in our pleasant leafy neighbourhood, and it is widely and readily available in that privileged seat of learning, Cambridge University itself.

While I’ve always believed the drug utterly ruins the lives of an unfortunate small minority — as a vicar’s wife in Fulham, West London, I’ve seen, first-hand, lives destroyed by it — Lara herself goes further. She maintains that it damages everyone it touches, even in the tiniest of amounts and for any length of time.

I always knew Lara was the last person who should have dabbled in drugs. Mental illness runs in our family: two of Lara’s cousins, of the same age, have had problems, and the links between schizoprenia, psychosis and cannabis are well-documented.

Lara, known as Bink to her parents, as she is today

An imaginative and eccentric child, Lara — whom we call Bink — was always quirky. But soon after she gained a place at the prestigious St Paul’s Girls’ School in London, aged 11, her quirkiness took a worrying turn.

Ostracised by a schoolfriend and desperately lonely, she started to worry about her personal cleanliness. This developed into a problem with obsessive washing. Unknown to us, she’d get up every day at 3 am to wash her clothes then go to school in them wet, so she could be ‘clean’.

At 15, with us growing increasingly concerned about her troubles, she was diagnosed with obsessive compulsive disorder by a psychiatrist friend. At 16, after waiting an agonising year for treatment due to an administrative error, she took a ‘gesture’ overdose in a desperate bid for help.

I knew that’s all it was — she’d called for help as soon as she’d taken the drugs — but suddenly the big guns of the medical profession took notice and said she must be hospitalised.

We had just settled her in hospital when the nurse dropped the bombshell: at 16 she was an ‘adult’, and we, her parents, had no rights. Not to take her home, nor to see her notes; not to visit — and certainly not to veto her treatment.

How often have I berated myself for not going straight back upstairs and telling her to pack her bags!

After that, we could only watch, appalled, as her condition worsened ten-fold: robbed of the intellectual stimulation of school and home, surrounded by patients with acute (and very different) mental illnesses, put in worse-than-useless therapy all day, denied fresh air and exercise and rake-thin within a week.

At least I knew she was as opposed to medication as I was.

But how long can you hold out, aged 16 and as vulnerable as a child, cut off from your family and with all the adults supposedly ‘caring’ for you, bullying you instead? After six weeks, Lara gave in and took the pills.

So began an addiction to anti-depressants which was to propel her, eventually, into the grips of an even more damaging drug: cannabis. Though she was never addicted to cannabis, she holds both responsible for the havoc wreaked in her life.

Over the next few years, with a few intermittent fits and starts, Lara managed to continue with school and gained a place at Cambridge to read English Literature.

But life was a monumental struggle: she was sleeping for 18 to 20 hours a day. Repeatedly, she asked her GP (as did I) why she couldn’t stay awake. It took a fellow undergraduate to tell her it was down to her medication.

So that Easter 2011, she gradually came off the drugs over six weeks. None of us knew how much she was suffering with withdrawal. But in daily agony, on the point of another breakdown and facing the loss of her university place — but determined not to go back on the medication which had done her so much harm — she looked around for something to get her through.

Lara gained a place at Cambridge to read English Literature, where she did manage to get a good degree

And that something was cannabis.

Of course, she kept it from us. She knew how passionately we were both opposed to it. Cannabis had never been part of our comfortable, middle-class lives, but we knew of the ravages it could wreak from a few unfortunate members of our parish.

To Lara, though, it became a lifeline. Easily susceptible, her tiny puff got her through each day. And, ironically, she says that it worked. It gave her a window in the pain, a few hours of relief. And, yes, despite sometimes clinging on to life by her fingertips, she got a good degree.

But, underneath, her personality was being eroded. Intelligent friends, her therapist and, most shockingly, a psychiatrist, all knew she was using it and didn’t stop her. The psychiatrist even asserted that alcohol would do more damage than cannabis.

What no one told her, however, was that it could also render her irresponsive, sometimes even mute, and incapable of seeing that her family loved her and longed to help.

She was, she says now, tormented and in hell. But the cannabis itself made her incapable of isolating the problem. She knew something was terribly wrong, but not what it was.

Within weeks of her starting to use it, I knew something was desperately amiss. Although she never smoked cannabis in front of me, I became more and more distressed as our previously gentle and kind daughter started to astonish us with some brutally unkind behaviour.

It seems so petty, but little things, tiny acts of selfishness and spite, told me something had robbed us of our lovely girl. One evening, I cooked her favourite curry for her and some friends who longed to meet her, but she didn’t bother to turn up.

Happier times: Anne with Lara when she was younger and her father Shaun

She never answered her phone, or apologised — and couldn’t see why she had to.

Back at university, she never rang us and she even started to live elsewhere. Her little sister Rose, now 13 and by far Lara’s biggest fan, couldn’t work out what was going on. Her sister had always had time for her; but now she had become an unreliable ‘fruitcake’.

Nevertheless, Lara looked stunning at her graduation and at her sister Serena’s wedding in the summer of 2013, although she spent the evening outside the marquee in tears.

She then planned to spend a month or two catching up with friends before joining the world of work. It never happened. She drifted, living off benefits, staying with friends, once sleeping rough for a month in a desperate bid to get treatment.

She had long since stopped using cannabis, realising the impact on her mental health, but the damage had been done.

Then came that call, in the dead of night, in November 2013. She’d left a strange note at a friend’s house, possibly suggesting suicide.

The police called us and we dropped everything to go to the hospital — where we were dismissed in a tirade of insults and accusations. All she knew was that she was in terrible pain. For the next two years, Shaun and I hardly saw our daughter, and sometimes we didn’t know whether she was alive or dead.

Most painfully, we had to tell Rose’s boarding school not to put calls through from her adored sister, or let her visit. We just didn’t know her any more. It was more painful than all her previous years of illness put together. Occasionally she would make contact, angry and unrecognisable.

Then one night 18 months ago, at 1.30am, she rang asking for help. Something had broken in her, and she wanted to come home.

Anne with Lara when she was a baby and elder daughter Serena

She’d been away for so long that for ages she’d felt she couldn’t come back. But she knew her only chance of getting well was to reach out and hope someone was there to catch her.

Of course, we were. I collected her immediately. We had never seen her so ill, frequently unable even to speak: but she was home.

Caring for her over the past year has not been easy, but our lovely daughter is slowly returning, though there is still a long haul before she will be able to fend for herself, let alone seek employment.

Two weeks ago she took her first step to independence, moving to supported accommodation in Cambridge. She speaks of her ‘four-year psychosis’, and is convinced that cannabis was the cause of her dramatic decline. Yes, her mental health problems were already there, but that in itself made her dangerously susceptible to the drug.

Currently, she says, we have the worst of everything: cannabis is both socially acceptable and unregulated. She maintains we need to make it safer and change society’s attitude. Not until cannabis has become as unacceptable as hard drugs will we really be getting to grips with it.

Lara has friends who will never recover from the effects of cannabis, living in hospitals for the rest of their lives. She considers herself extremely lucky to have come back from that place. As a child, Lara dreamed of being a writer — and a mother. But after her terrible experiences, part of her is frightened of passing on the illness she inherited.