More people using drugs isn't automatically undesirable, as more people abusing drugs is.

Too often drug use is equated with drug abuse, but it need not be so. It's possible to use drugs and not have them affect your life negatively, or even have them affect your life positively (as in the case of the various psychedelic therapies out there to tread everything from PTSD to depression, using psychedelics to enhance one's creativity or for problem solving, or arguably psychedelic use in sacramental/religious contexts).

Another thing to consider when looking at raw statistics that might show an increase in drug use is that people are more likely to honestly report their drug use if they think they won't be punished for it, and conversely are more likely to lie about it if they thought they might get punished or stigmatized for it. In the case of Portugal, their non-punitive approach increases the odds that people will be more honest about their drug use, so the apparent increase in drug use might be just surveys finally reporting the truth about already-existing drug use. Real drug use there might have stayed the same or even decreased while showing an increase on paper.

Rates of injecting drug use have decreased.

Drug use in adolescants have decreased.

Rates of harm have decreased dramatically.

I question the measurements of harm, which I believe in the Portuguese case is in terms of diseases/hospitalizations/deaths. Everyone knows high-functioning people who have alcohol or drug problems, who will probably not show up in such measurements of harmful use, but who nonetheless suffer personal and family problems due to their habit.

Also, this article, though a little dated, seems to contradict your claim about drug use in the last 12 months.

https://www.npr.org/2011/01/20/133086356/Mixed-Results-For-P...

>While people reporting drug use over the course of their lifetime has gone up, somewhat significantly in the last decade in Portugal, people reporting drug use over the last 12 months of their lives has actually gone up only slightly.

And again, Portugal didn't have much of a drug culture to begin with. Where drug use is a much greater and ubiquitous cultural phenomenon, like in the US, it is very plausible that decriminalization would lead to significantly increased use.

There's not much point continuing the conversation if you're going to cite 6 year old radio interviews between journalists who don't bother to cite their sources.