Many people seriously addicted to fentanyl have already died in San Francisco, and those who are still alive increasingly have access to Narcan and have learned what their limits are, which experts say are both reasons why the number of fatal overdoses has declined.There have been headlines the past couple of months celebrating new low numbers of overdose deaths in San Francisco, something that has been counted a win for public health measures like widespread distribution of the overdose-reversing drug Narcan/nalaoxone. In October, the city recorded 32 fatal overdoses, which certainly still seems like too many, but it is the lowest number since the city began tracking these figures monthly four years ago.The fentanyl crisis remains relatively new, both here and elsewhere in the country. The drug only gained prominence over other drugs like oxycodone and heroin in the US black market a few years ago, owing to its incredible potency and cheapness, leading to the dystopian scenes we see play out in urban centers around the US.But there are signs, including the decreasing fatal overdose figures, that both our city and the rest of the country has reached an inflection point.As the Chronicle reports today, after speaking with multiple public health and addiction experts locally, a few factors seem to be at play in causing the overdose numbers to abate.For one, paradoxically, the introduction of Tranq or xylazine in the drug supply appears to cause less severe overdoses. And, because xylazine causes users to get terrible skin lesions and infections, they may end up doing it less often. Researchers who have been tracking drug users in areas where xylazine is more prevalent than here, including Pittsburgh and Grand Rapids, have found users saying that xylazine prevents withdrawal from happening as quickly — and along with the skin lesion issue, ends up causing them to use less often.Availability of methadone and buprenorphine, which are both used to treat opioid addiction, along with new behavioral health options, have led to an increase in drug users seeking treatment, according to the SF Department of Public Health. The number of users checking into treatment facilities locally is up 21% compared to last year. And while just over 200 people sought treatment in the fourth quarter of 2023, that number rose to almost 300 in the most recent quarter.Users may be learning to be smarter about their use after more experience with fentanyl, health officials say. But there is also evidence that the fentanyl-user population itself is shrinking. While existing fentanyl users are getting older — or, in some cases, dying — not as many younger users are replacing them, experts say."As there’s more death and destruction, people are losing people they know, seeing this incredible damage... It lowers people’s willingness to initiate drug use," says  Keith Humphreys, an addiction researcher and a professor of psychiatry at Stanford, speaking to the Chronicle. "Over time, that shrinks the vulnerable population."Researchers saw a similar phenomenon with the crack epidemic of the 1980s and early 90s — it faded out not because of government intervention, but mostly because younger people saw the drug's negative effects in their communities and weren't doing it, choosing to experiment with other drugs like marijuana instead.Nationally, overdose deaths, many of them fentanyl-related, peaked in 2023, and also are coming down. Fatal overdoses are down 15% since last year, nationally, and down 10% in California, though these numbers are still provisional, as the Chronicle reports via the CDC. Part of this decline, experts say, is also the end of the COVID pandemic, during which individuals were more isolated, and the number of overdoses skyrocketed.Related: SF Overdose Deaths Hit Promising New LowTop image: A photo of "rainbow fentanyl" from the Placer County DA's Office