Not a magical solution

Here's an interesting, (though of course, inconclusive) study that gives some reason to be skeptical of those overstating the value of psilocybin as a future medicine: 

More than 2,300 psilocybin users report real-world outcomes in Oregon and Colorado 

Some extracts:

While many clinical trials have yielded promising results, they might not reliably reflect how different people could respond to psychedelics. This is because participants who take part in clinical trials typically undergo extensive prescreening, and many others who might wish to access regulated psilocybin services are excluded.

Under state law, Oregon and Colorado now allow eligible adults 21 or older to take psilocybin under the supervision of licensed facilitators at regulated centers. Both states require clients to undergo screening, although their eligibility criteria differ. In Oregon, clients may be ineligible if they are experiencing thoughts of harming themselves or others, have taken lithium within the previous 30 days or have ever been diagnosed with active psychosis. Colorado requires a general safety screening and allows facilitators to decline clients for health or safety reasons.

Researchers at the University of Colorado Anschutz School of Medicine and Althea PBC recently carried out a study examining the experiences of people who received psilocybin at licensed service centers in Oregon and Colorado.They summarized their main findings and observations in a paper posted on the medRxiv preprint server....

 

Over a period of 15 months, Althea compiled a database containing data provided by 2,363 individuals who had received psilocybin at licensed centers. This included their demographics, reasons for seeking psilocybin, prior medical histories, the dose they received, the quality and intensity of their subjective experience (i.e., the trip), any adverse events during and after dosing, and changes in their mental health after they received the drug.

"Fifty percent of participants were 'psychedelic tourists' traveling from out of state to receive psilocybin," said Thompson. "Thirty-six percent of participants were motivated to seek psilocybin because of mental health concerns. The mean dose of psilocybin received was 29 mg, comparable to a standard clinical trial dose of 25 mg. We found that people's depression (assessed with the PHQ-9 questionnaire) and anxiety (assessed with the GAD-7 questionnaire) scores decreased by about 50% at 2 weeks after dosing, also comparable to clinical trial results."

The team's analysis of the collected data also showed that the intensity of people's subjective mystical-type experiences was only weakly correlated with improvements in anxiety or depression. This means that more intense mystical experiences during dosing did not necessarily correspond to better mental health outcomes.

Receiving psilocybin was associated with improved mental health scores in more than half of the participants who completed the relevant follow-up questionnaires. Specifically, 50% to 60% exhibited reductions of at least 50% in their depression or anxiety scores two weeks after dosing.

"Depression and anxiety improvements were the same for those receiving more than 30 mg or less than 30 mg of psilocybin," said Thompson. "Although subjective effects were lower, benefits were comparable in people taking selective serotonin reuptake inhibitors (SSRIs), suggesting weaning is not necessary. Adverse events were mild and transient (nausea, anxiety, headache), as in clinical trials, and there were no reports of novel psychosis, although suicidality results were somewhat ambiguous."

The actual paper notes:

There were 94 mild adverse events during and after dosing, five more serious events not clearly related to treatment, and evidence of possible risk of increased suicidality. Study limitations include open label administration, self-reporting, loss of participants for follow-up, and a short 2-week post-dosing end-point. We conclude that psilocybin services, delivered within these regulated frameworks, is associated with improvements in mental health in real world populations, however, more robust monitoring is needed to ensure safety. 

As to the suicide ideation effect, I find it hard to understand these numbers:

Suicide. Of 1476 respondents at baseline, 18 participants endorsed self-harm concerns, 44 had
thoughts of suicide, and 87 reported a prior suicide attempt. All received psilocybin. Adverse
events for these participants were four reports of nausea on the dosing day, one report of
crying on dosing day, and one report of nausea the day after dosing.

We also analyzed responses to the PHQ-9 regarding suicidal ideation and considered responses of nearly every day, more than half of days, or several days to be indicative of suicidal risk. Of 371 respondents, 95 expressed suicidal risk in the two weeks preceding their baseline assessment. 28 of these 95 participants responded before and after dosing, of which 22 reported a decreased frequency of suicidal ideation after dosing and 6 reported no change. Of 103 participants who reported no suicidal ideation at baseline, 11 did report suicidal risk two weeks after dosing. Total PHQ-9 scores were increased or unchanged in eight of these 11 after dosing.

 I don't know - but the line in bold sounds like in one group of no suicide ideation before dosing, suicide risk did happen in 10% of them in the two weeks following?

As I say, it's hard to understand.

And, of course, the positive effects overall have only been measured for 2 weeks, in a group of people who self selected to try this.  Also, no placebo group involved (although, as this article noted, it's pretty much impossible to do placebo control groups when testing the effects of psychedelics, for obvious reasons!)   

Anyway, I asked Claude AI about the issue of what percent of people being affected by a suicidal ideation side effect would it take to restrict the use of a drug for depression.  It said there is no set formula, and it all comes down to risk/benefit assessments, but it did include this (apparent) specific example:

The classic example here is the FDA's 2004 warning (later a boxed warning) on antidepressants (SSRIs and others) regarding increased suicidal thinking/behavior in children, adolescents, and young adults (up to age 24) during the initial months of treatment. This came from a meta-analysis showing roughly a doubling of risk (from about 2% on placebo to about 4% on drug) in that age group — not a "too high, pull it" number, but a "warn, monitor closely, especially early in treatment" response. The drugs stayed on the market.