The National Advisory Committee on Drugs said investment in drug detoxification programmes is paying off.
It says new research shows that taking part in the treatment programmes does help reduce dependency.
More than 400 drug users took part in the study, which followed their progress over the course of a year.
Completion rates were high with more than two-thirds finished the detox courses.
Participants' use of heroin, cocaine, and alcohol fell in terms of numbers reporting use, frequency of use and the average quantity of each drug consumed.
One year on, three-quarters said they were not involved in any kind of criminal activity - up from just 19 per cent at the start.
And in addition both their mental and physical health was much improved.