A 30-year-old man who was addicted to a legal herbal drug bought on the internet has died after it caused major heart problems.

The inquest into the death of Oliver Cohen, who grew up in Borehamwood, found last Wednesday that his two-year addiction to kratom, along with other drugs, led to heart failure.

His mother, Janet Koganovitch, of Manor Way, is campaigning to stop people buying unprescribed medicine online.

She said her son suffered from attention deficit hyperactivity disorder (ADHD) and had been ordering a herbal supplement called kratom from an online company to help ease his symptoms.

Kratom, an opium substitute derived from the leaves of Mitragyna speciosa, a tree native to Southeast Asia, is widely used overseas as a natural stimulant. It is not banned in the UK but is not prescribed by doctors.

One UK website boasts that kratom is “the world’s most effective herbal legal painkiller and herbal high”.

Ms Koganovitch said: “He didn’t think anything would happen to him. He thought he knew best.

“He was quite hyper and found it difficult to concentrate on his work. He wanted to become a musician but he couldn’t focus enough. At the time [of his death] he was working on his business — he was very into his music.

“He felt this [kratom] was helping him in the beginning. It was only over time that he became addicted to it.”

Ms Koganovitch’s persistent warnings about the risks of buying drugs online failed to convince her son.

He had developed insecurities about his slight frame and was also taking steroids, also bought online, to bulk up.

“He convinced me that if it’s taken occasionally it wouldn’t do any harm,” she said. “I always used to say to him, ‘be careful, you don’t know what you’re getting online. Go to the doctor if you need help’.

“He used to say to me, ‘stop worrying, they’re harmless, they’re not going to do anything, they are helping me with my work and I can’t work without them’.”

Ms Koganovitch says more people are using websites to buy substances such as kratom, as thrill-seekers look to experiment with new ways of getting a high.

“Teens are looking for something new — ecstasy and other, similar, drugs aren’t enough anymore. They’re looking for something else now.

“Oliver was looking for new things all the time.”

Ms Koganovitch said a near-death experience following an overdose failed to wean Mr Cohen off the drugs.

She added: “He said to me after that, ‘this is very selfish, it’s terrible what I’m doing.’ I stressed to him how valuable life is and he promised me many times he would stop.”

He eventually died from heart failure, at the QEII Hospital in Welwyn Garden City, a month after celebrating his 30th birthday.

Ms Koganovitch concluded: “It’s more dangerous buying something online than buying anywhere else, because you don’t know what you’re getting or what’s in it.

“Parents need to talk as much as possible to their kids to make them aware of the dangers.”

Recording a verdict of misadventure at the inquest last week, coroner Edward Thomas also pointed out the dangers of ordering unprescribed medication over the internet.

He said: “It’s so important that what people take is properly prescribed. The implications of not doing this can be very serious.”