a) it is based on the writing of L. Ron Hubbard, considered a liar and a quack;
b) its materials lack quality and trustworthiness;
c) there exist no independently recognized studies which confirm the efficacy of the rehab program, and
d) it is linked to the Church of Scientology in such a way that it considered one of the cult’s front groups. (TIME magazine has referred to Narconon as “a classic vehicle for drawing addicts into the cult.” )
The publishers of Apologetics Index consider the Church of Scientology (including its related entities) to be a commercial enterprise that masquerades as a religion. In our view Scientology preys on vulnerable people through a variety of front groups, including Narconon (which operates in some prisons under the name “Criminon”).
In our opinion Scientology’s medical teachings — based as they are on the writings of founder L. Ron Hubbard — amount to a mixture of fantasy, lies and quackery. 
Wikipedia puts it this way:
[Narconon’s] drug rehabilitation treatment has been described as “medically unsafe”, “quackery” and “medical fraud”, while academic and medical experts have dismissed its educational programme as containing “factual errors in basic concepts such as physical and mental effects, addiction and even spelling.” 
We encourage those who are addicted to narcotics or other substances to not get involved with Scientology or its front group, but to instead contact legitimate organizations, such as Narcotics Anonymous
The United States Internal Revenue Service, as a condition of its 1 October 1993 tax-exemption agreement with the Church of Scientology, sent to foreign governments an official “Description of the Scientology Religion” produced by the Church of Scientology International. It gives the following concise description:
Perhaps the lowest point in David Love’s “treatment” for drug addiction at Narconon Trois Rivières was the five-hour sauna on his 25th day of five-hour saunas.
Being forced to yell at an ashtray for hours on end – “Stand up, ashtray!” “Thank you.” “Sit back down, ashtray!” – also left him confused and frustrated. But it was when Love realized that the rehab centre inspired by the teachings of Scientology was actually putting vulnerable addicts’ health at risk – and that he had become a part of the machinery – that he decided to get out.
On Oct. 28, 2009, six months after he had gone from “graduate” of the Narconon program to “Certified Counsellor,” Love left the facility and began a crusade to have it shut down. In July 2011, following his complaint, the Quebec College of Physicians ordered Dr. Pierre Labonté, Narconon’s “medical manager,” to cut his associations with the centre, located about 125 kilometres northeast of Montreal. The Quebec labour relations tribunal also mediated in Love’s favour when he complained about being paid $2.50 an hour as a staff member.
Then last Friday, 2½ years after Love began his campaign, public health officials for the Mauricie region ordered Narconon to relocate its 32 residents and told the organization they would not certify the centre, because its approach was not recognized in this province, and that its practices, including the saunas and massive doses of niacin, were potentially putting patients’ health at risk.
Most of the patients, from B.C. and other provinces as well as the United States, have since been relocated to Narconon centres in the U.S.
As for David Love, he remains drug-free since he left Narconon – but deeply traumatized by what he saw and went through in Trois Rivières.
Top Scientology officials at the church’s nerve center, the Religious Technology Center, deny any connection to Narconon.
“The definitive answer is RTC doesn’t have anything to do with them,” RTC President Warren L. McShane said in a letter to the Herald.
“I’ve checked my files, we have never had a licensing agreement with them or any secular group,” McShane said.
But the RTC clearly states on all Scientology literature that the Purification Rundown is a registered trademark used only with its permission.
Also, L. Ron Hubbard’s name is trademarked by the RTC, and all his books are copyrighted by another key Scientology organization called the L. Ron Hubbard Library. Hubbard’s name and his writings may only be used with permission, according to numerous Scientology publications.
Robert Vaughn Young, a former top Scientology official, said it is common knowledge among top Scientologists that the RTC strictly controls Narconon through licensing agreements.
Also, church documents say the RTC is “protector of the religion” ensuring “purity of application” of Hubbard’s teachings, with an “Inspector General Network” to enforce RTC rules.
State Superintendent Jack O’Connell urged all California schools on Tuesday to drop the Narconon antidrug education program after a new state evaluation concluded that its curriculum offers inaccurate and unscientific information. […] Scientology correspondence obtained by The Chronicle said Narconon’s instruction is delivered in language purged of most church parlance, but includes “all the Scientology and Dianetics Handbook basics.”
Inside Apologetics Index: