The spike in treatment referrals came despite an apparent decrease in supply of illicit drugs.
There was a large decrease in drug seizures by Customs in April and May, with meth seizures down 65 per cent, cocaine seizures down 98 per cent, and MDMA down 58 per cent.
The survey showed 65 per cent of drug users reported a decrease in drug availability during lockdown.
The report also shows despite an amendment to the Misuse of Drugs Act last year, illicit drug convictions do not appear to be slowing.
The amendment aimed to reduce the number of unnecessary convictions by solidifying into law the police's existing discretion to only prosecute for possession or use of drugs if it is "required in the public interest".
"While the total number of court actions for possession offences went down slightly in the 10 months since the law change, the total number of proceedings actually rose due to an increase in warnings issued," Mercier said.
In 2019/20, 3067 people were convicted of low-level drug offences, and for 1126 people, the drug conviction was their most serious offence, she said.
"Of those convicted, almost half were under 30 years, 71 per cent were men, and Māori made up 39 per cent."
Cannabis convictions continue to decrease, however, with methamphetamine convictions overtaking cannabis for the first time ever in 2019/2020.
Overall the report shows steady rates of harmful alcohol use, as well as an increase in those using cannabis.
"Methamphetamine use remained steady, and although only a very small percentage of the population use this substance it continues to be of concern. MDMA use has increased. However, alcohol continues to be the drug causing the most harm in New Zealand."
A third of New Zealanders have a moderate to high risk of experiencing health and other problems from their substance use - mostly from alcohol and tobacco.
"Today's report continues to demonstrate that we need increased funding for treatment and early intervention as well as a step change in the way we deal with drug use in New Zealand. Other countries, such as Portugal, have shown a health-based approach can significantly reduce harmful use, and use among young people," Mercier said.
"We know the Government sees the importance of treating drug use as a health issue. Their decisive action last week to legalise drug checking at festivals shows they get it. And this change was met with a positive response, showing most New Zealanders get it too. But that was just one piece of the puzzle."
This is the third State of the Nation report published by the Drug Foundation. Figures are collated from a range of public sources and data obtained via the Official Information Act.
