Hundreds of young children are being admitted to hospital for drug and alcohol overdoses every year, with some as young as seven arriving at hospital drunk on wine.

Documents obtained under the Official Information Act from 13 district health boards around New Zealand paint a shocking picture of very young children having to be treated in hospital for the effects of drugs and alcohol.

Many of these are accidental poisonings from medicine or household products, alongside preventable cases in which life-threatening amounts of illegal drugs and alcohol have been taken by – or given to – young children and teenagers.

They include a 10-month-old baby who arrived unconscious at Palmerston North Hospital and whose urine was found to contain traces of P and cannabis, several cases of toddlers treated for cannabis overdoses at Whangarei Hospital, and extremely intoxicated pre-teens – as young as seven – arriving at hospitals nationwide.

In Wellington and Kenepuru hospitals, 70 children between the ages of 13 and 18 have been classified as having some kind of drug or alcohol addiction since 2001.

At Auckland Hospital, records show dozens of drunk 12-to-15-year-olds admitted with head injuries, open wounds and dislocated bones. Hospital notes show them collapsing and vomiting, in various states of consciousness.

In 2007 a seven-year-old arrived drowsy and drunk on wine, and this year a 13-year-old was in hospital for eight days to treat injuries suffered in a "high fall" while drunk.

In the past five years, nationwide, 23 young people have died from drug and alcohol overdoses.

Auckland Hospital clinical director of child health Richard Aickin said incidences of intoxicated children younger than 15 appeared to be an "early experimentation event", rather than an established pattern of behaviour.

Most admissions among this age group were toddlers who drank or ate a medicine, household chemical or plant they found lying around.

Most alcohol use in children was in the 15-to-18 age group, along with many incidences of intentional drug poisoning.

Auckland Community Alcohol and Drug Service youth addiction psychiatrist Grant Christie, who treats alcohol-dependent teens aged 13 to 18, said drunk and drugged young people ending up in hospital were just "the tip of the iceberg".

About 500 teens were referred to the service last year, and he was seeing more – and younger – each year.

"Most young people with severe problems don't end up being hospitalised and only a few actually get the treatment they need.

"The levels of some young people's use is quite staggering: many would see buying a box [24 cans] of beer – or a bottle of spirits, or a cask of wine – to drink over the course of an evening as pretty standard."

Children's Commissioner Russell Wills, a Hastings Hospital paediatrician, said illegal-drug and alcohol overdoses among very young children were, thankfully, rare.

"When it happens it is shocking and terrible ... The families are almost always very complex. The children will commonly have parents who have major drug and alcohol issues; they will commonly have mental issues, very poor support, chaotic lifestyles, violence, poverty – the whole package.

"It often requires multiple agencies to wrap around the family, and find out what's going on and what's fixable."

Youth Affairs Minister Paula Bennett said: "I'm personally extremely concerned whenever I hear about horrific cases of very young children in particular being exposed to drugs and alcohol. Let's be clear, at best this is neglectful parenting, at worst it is serious child abuse."