Is it true that addiction treatment curbs the spreading of diseases such as HIV and AIDS?

If so, then how does it do this?

I think addiction treatment does decrease the spread of HIV and AIDS. This is due to the fact that drug users are the people who are likely to get afflicted with such illnesses. When a person is doing drugs, he is the one more likely to engage in unprotected sexual activities and thus may do it with a partner who has a sexually transmitted disease. The sharing of drug paraphernalia such as needles are also reasons why HIV and AIDS are transmitted to drug addicts. Hence, treating drug addicts will get to help in lessening the spreading of HIV and AIDS. Researches have even shown that the drug addicts who don't let themselves get treated for their addiction are up to 6 times more likely to get afflicted with AIDS or HIV, compared to the ones who let themselves undergo treatment.

Maybe it's curbing the use of needles that are common in addictions?

Not for the most part. AIDS can really only be stopped by stopping promiscuity and corrupt behavior, especially homosexual practices (which brought it into the world).

twofold, the first answerer had a really good argument about drugs and promiscuity, so i won't touch that again.

also, if the users are doing injectable drugs they run the risk of spreading HIV and AIDS by sharing needles.