It all began when he first purchased the drug, and got worse as he dropped out of tertiary education and lost valuable connections with family and friends.
The downward spiral continued, coming to a head at the start of this year when he upped his dosage in order to feel the same "high" as before. Finally, after numerous failed promises to stop using, he realised how his addiction was harming the other people in his life.
"We are just an ordinary family, there was a lot of shame attached to this," Mrs Vandenberg says. "We didn't realise it could affect us, an average middle class family who have instilled a lot of good values in our children."
Having no experience with addiction in any form, the journey through this dark time was completely foreign; it was particularly hard on his three siblings and parents who had no option but to watch him morph into a completely different person.
"He was just skin and bone, he was just so undernourished, he was living on the streets. He came home for a while but the stress was immense. It was difficult to deal with the psychosis - he was crying and destroying things, we had to call the police because we feared for our safety. Because of suicidal thoughts he ended up in hospital, but if he had kept going the way he was, he could have died, I have no doubt about that."
Today, he faces a long road to recovery but painful reminders of his habit remain - medical tests show damage to his liver and he suffers from memory loss; there is also plenty of grief and regret over some of the decisions he has made.
As a private person it was a tough decision to come forward and tell her story, but Mrs Vandenberg decided before yesterday's rally that's exactly what she would do.
Meanwhile, Napier city councillor and mayoral candidate Bill Dalton found himself the centre of a police callout yesterday as he conducted a snap poll of apparent buyers and users of legal highs outside a central city shop.
Invited along with Napier MP Chris Tremain to see first-hand the extent of the trade in the shop's Dickens St neighbourhood, Mr Dalton arrived early. He began asking people about their involvement, ranging from a woman who said her boyfriend smoked several packets a day, and she wished he would stop, to someone who said the only alternative was death, a person who said it was financed by crime, and two abusive boys.
Police were called by the proprietor complaining Mr Dalton was obstructing members of the public, and patrols were still at the scene when Mr Tremain arrived. Last night Hawke's Bay Today understood no action was taken against Mr Dalton, but witnesses saw police speaking with apparent users or buyers.
