Zentveld was admitted to Lake Alice five times, for a total period of nearly three years.
In an "advance unedited version" of the decision, the UN committee recommended the New Zealand government conduct a "prompt, impartial and independent investigation" into all allegations of torture and ill-treatment at Lake Alice.
The decision also recommended, where appropriate, the filing of "specific torture and/or ill-treatment charges against perpetrators, and the application of the corresponding penalties under domestic law".
In 2010, police investigating allegations by 40 people announced that no criminal charges would be laid against Dr Selwyn Leeks, who headed the child and adolescent unit.
On 29 December 2019, two days after the advance version of the recommendation was released by the UN, the Abuse in Care Royal Commission of Inquiry announced it would investigate the allegations.
But the commission would not make findings "civil, criminal or disciplinary liability", as was recommended by the UN.
Zentveld described the UN's decision as "a victory for the little people" and "history in the making".
"It was a long road and we had to stay positive, and the outcome was awesome."
He said the onus was now on the government to act.
The complaint to the UN was submitted in July 2017 by Victor Boyd of independent watchdog group Citizen's Commission on Human Rights (CCHR) on behalf of Zentveld.
CCHR New Zealand director Mike Ferriss called the decision "monumental".
"It fully supports what Lake Alice victims have been wanting all along - to bring to justice those responsible for the psychiatric abuse of children using an ECT machine and drugs".
- RNZ