His parents put him in hospital but once there he tragically hanged himself

But he started smoking cannabis and the 'harmless' drug took its toll

Melanie Leahy has many photos of her son, Matthew. But it is the one of him aged 13, fresh-faced and dressed in his grammar school uniform, that is the most painfully poignant of all.

'Matthew had just been awarded top marks in all his academic subjects and was on the cusp of adulthood, with his whole future ahead of him,' she recalls. 'Even as a boy he spoke about his future, of having a large family and how he wanted to start up his own business.'

Happy and healthy: Matthew was 'gorgeous' and capable, learning to swim at the age of three

Tragically, it is a future Melanie will never see for her only child. For Matthew, 20, previously a Grade A student as well as an expert skiier and qualified lifeguard, hanged himself last November. His suicide was triggered, doctors believe, by smoking cannabis.

Any suicide is an utter tragedy, but what makes Matthew's case even more shocking is that the young man took his own life while an in-patient at a mental health hospital.

Despite being on hourly observation because of his unstable state of mind, Matthew had managed to hang himself.

'When I got the phone call to tell me about Matthew's death, it ripped my heart out,' says Melanie, 48, a property manager. 'But most of all I was in shock about how doctors could have allowed it to happen.

'Matthew's father, Michael, and I had agonised over putting him into that hospital. We believed he was in the safest possible hands and that we had done our best for him. We never would have agreed if we'd thought we were sending him to his death.' Melanie questions his treatment at the NHS-run Linden Centre mental health unit in Chelmsford, Essex.

Bright-eyed: Matthew, pictured in his school uniform, aged five - several years before his troubles began

Several other young people have taken their own lives while in the care of the trust in recent years and Matthew's parents are still waiting for answers as to what really happened to their beloved boy.

It's cannabis, a drug many class as 'harmless', that they blame for his spiral into self-destruction.

Born in December, 1991, Matthew was a 'healthy, happy and bright lad' according to his mother.

'Matthew was absolutely gorgeous and it soon became clear he was very bright,' says Melanie, who lives in Heybridge, Essex. 'He learned to swim at the age of three and, by time he was nine, was excelling academically at school.' Sadly, it was around this age that Melanie and Michael, a restaurateur, divorced.

'We'd been growing apart for a long time,' she explains. 'But where Matthew was concerned, we remained amicable, sharing care of him.'

Although Melanie and Matthew moved ten miles away to a three-bedroomed semi-detached home, Matthew divided his time between his parents' homes.

Painfully poignant: Of her many photos of Matthew, this one reminds Melanie the most of his bright future - now tragically lost

'We were incredibly proud when Matthew passed his 11-plus exam and won a place at Westcliff High School For Boys, a selective grammar school. He excelled at maths and science and was a natural with computers,' Melanie says. However, by the age of 14, teachers reported that Matthew wasn't paying as much attention at school.

Because of the characteristic smell of cannabis on his clothes, and his erratic behaviour, both Melanie and Michael suspected he was smoking the drug.

'I confronted him about it, but he would deny it,' says Melanie.

In June 2005 - after a friend told Melanie she'd seen him in a park smoking cannabis - Melanie took Matthew to see their GP.

'I wanted him to be tested,' she says. Her GP refused, on the grounds that it was not something GPs would test for, but Melanie became increasingly concerned about her son's behaviour.

'We had lots of arguments about him smoking cannabis. Both Michael and I did everything we could to try to stop him, from arguing to reasoning with him but nothing worked.'

By the age of 15, Matthew was having problems sleeping.

'Matthew saw his GP on his own and I now know from his medical notes that he admitted he was smoking cannabis, although because his friends were also smoking it he told his GP he believed it was harmless,' says Melanie.

'This time the doctor advised him about the risks and gave him advice about stopping smoking.'

But Matthew continued and, by the time he was 17, having left school with a clutch of GCSEs and the equivalent of two A-levels, he began his own computer support business. He moved into a shared house that Melanie owned, but at the same time his symptoms worsened significantly.

'Terrifyingly, he began saying he felt as if something was crawling over his body,' recalls Melanie. 'I researched it and pointed out to Matthew it was an effect of cannabis smoking [doctors call this sensation 'formication' and it is one of a number of hallucinations cannabis can trigger].

'Matthew saw his GP on his own and I now know from his medical notes that he admitted he was smoking cannabis, although because his friends were also smoking it he told his GP he believed it was harmless'

'It became so severe that, at the end of 2009, he was referred by his GP to the drug and alcohol early intervention team. They came and spoke to him about the effects of cannabis.'

Melanie now feels they didn't do nearly enough and wishes they'd referred him for counselling and more specialist help, such as drugs rehabilitation.

Matthew's parents grew even more concerned when, in January 2011, Matthew became convinced he had threadworms living in his stomach, coming out of his nostrils and mouth and living in his ears - a sign of the paranoia caused by the cannabis.

The drugs team explained he was delusional and Matthew's state of mind deteriorated so much he was unable to continue his computer job.

'Eventually in May, Matthew was in so much distress about these imagined parasites that it was preventing him from sleeping properly,' says Melanie. 'His GP felt he was hallucinating due to his drug problem and referred Matthew to a consultant psychiatrist.'

Yet he continued to smoke cannabis and his paranoia only worsened.

That June, having experienced a terrifying psychotic episode where he believed worms were destroying him, Matthew was admitted to the psychiatric ward at Clacton hospital and then the Linden Centre, where he remained for five months.

Young promise: 15-year-old Matthew, pictured with his mother Melanie, excelled at maths and science and was a natural with computers

Matthew was given drugs to calm his paranoia, but when he was released in November 2011 the family were shocked at his appearance.

'My son had become like a zombie,' says Melanie. 'He'd gone from a bright conversational boy to someone who was hollow-eyed, dribbling and shuffling.

'In hindsight, I don't feel there was any proper care for him at that hospital. His problems were just masked with medication and he was able to continue smoking the drug. I was horrified by the smell of cannabis whenever I visited him.'

His problems were clearly far from resolved when, in April 2012, Matthew - by now back in the shared house - erupted at Melanie when she forbade him to grow cannabis there.

'He said he couldn't deal with the hallucinations any more and wanted to kill himself,' she says. 'He thought the cannabis was helping to cure them, and wouldn't believe it was the cause.

'He threatened to cut his wrists or hang himself and I was so upset I called the police who took him to hospital.' Over the following weeks, Melanie's life became hell.

'One day, Matthew came home with cuts on his face that he'd made with a razor blade. He then threatened to hang himself. I kept telling him I loved him and begged him to get help.

'Another time when I wouldn't give him any money because I knew he would spend it on cannabis, he pinned me against a wall. I wasn't hurt, but it was frightening. I rang the police and, once again, they returned him to hospital.'

Heartbreak: Melanie keeps the memories of her beloved son close to her heart

Melanie's frustration with the system is evident. 'Despite all these episodes, he would simply be taken to hospital by police, be assessed and just sent home again,' she says.

In May 2012, with Melanie at her wits' end, Matthew, now 20, went to live with his father. But in November 2012, during a terrifying psychotic episode at his father's home in Bradwell, Essex, he smashed up his room with a baseball bat.

Michael says: 'Matthew was threatening to kill himself with a knife, so I called the police. He was in such a rage there was no knowing what he'd do.'

At this point he was admitted to the Linden Centre under Section 3 of the Mental Health act.

'Melanie and I were desperate,' explains Michael. 'Matthew needed professional help. He needed proper care and, although it was the hardest thing we've ever done, we believed putting him in hospital would save him.

'We were terrified that, if we didn't section him, he would kill himself. Doctors told us Matthew would be put on suicide watch, which reassured us because we felt something positive was being done at last.

'It was exhausting for us watching his every movement 24 hours a day and we knew this way he would not be allowed to kill himself.'

'My son had become like a zombie. He'd gone from a bright conversational boy to someone who was hollow-eyed, dribbling and shuffling. In hindsight, I don't feel there was any proper care for him at that hospital. '

However, the couple say they have since been told that Matthew was put on constant watch only for the first day. They say they've been told this was reduced to hourly and he was being watched by a student nurse.

'We have no idea why this was allowed to happen, it was a decision made by the nurses,' says Melanie. 'But, had I known that he wouldn't be watched 24 hours a day, I would never have agreed to let him go. I bitterly regret it.'

Tragically, five days before his death, Matthew rang his father, distraught, saying he'd been drugged and was desperately unhappy.

'We were scared for him, but were told not to visit for first seven days to give him time to settle,' says Melanie. 'And when we spoke to the ward, the staff denied he was as distressed as he'd made out to us, reassuring us he was in an art class.'

A post-mortem examination has since also revealed four to five mystery needle marks in Matthew's groin.

'He was petrified of needles,' says Melanie. 'We worry as to what drugs he had been injected with. We've had no explanation as to what these were, but it haunts me that he might have experienced real terror in those final days.'

Melanie was shocked to discover that Matthew was not the only troubled young person to die in the care of the same trust.

Grieving parents: Melanie and Matthew's father Michael now bitterly regret putting their son in hospital

In 2001, Nicola Dordoy, 42, was found hanging from her curtain pole in her room at the Linden Centre, prompting the unit to claim that 'procedures would be changed' as a result.

A year later, Steven Kay, 39, went missing from his room at the Linden Centre and was later found hanging from a tree. Then, in 2008, Ben Morris, 20, hanged himself with his belt at the same centre.

In May 2012, a Care Quality Commission report judged over all that 'the Linden Centre was not meeting one or more essential standards. Action is needed.'

Says Melanie: 'I was stunned by the fact that similar problems over lack of care plans, risk assessments and communication errors had been highlighted so many times at the same centre and the same trust.

'Had the trust taken on board all the issues then and improved the care within these mental health units, I believe Matthew would still be alive today.'

She claims that a lack of records of Matthew's final days might mean she never knows exactly what happened to her son.

North Essex Partnership said: 'What happened to Matthew is terrible and the family's hurt is totally understandable. Everyone wants answers.

'The coroner can hold an inquest where all issues are raised, and questions asked. We ask Melanie and her family to talk to us about it all, we will answer her questions and her fears, frankly and honestly. That's in everyone's interest.'

Almost a year on, the family are still waiting for an inquest, but they bitterly regret putting him the hospital.

'Losing Matthew has caused pain beyond description,' says Melanie. 'But I'm not going to be happy with weak promises for the future.'