Hi everyone,
Researchers followed 11,036 American kids from age 9 to 17, and the ones who started using cannabis stopped gaining thinking skills at the pace of everyone else. Memory, processing speed, self control, language, all of it flattened out. Those kids were doing fine, or a little ahead, before they started. I also found a few other studies worth your time: psilocybin for stubborn depression, MMR timing in 2.5 million children, a hospital antibiotic practice tied to higher 90-day mortality, and a vitamin D result that did not hold up. Plus a podcast on building muscle with light weights and a set of cuffs.
Quick note before we start. One thread running through this issue is that there is rarely a single pill that fixes a complicated problem. A megadose of vitamin D did nothing for advanced colon cancer, and the work stays with the daily inputs instead. Blood sugar is one of the clearest examples of that, and if steadying yours is something you are working on, whether it is prediabetes, diabetes, or just the afternoon crash that keeps showing up, Clarity uses AI to build a plan around your own situation and then coaches you on it day to day. Take a look below. It is a product I recommend, and it is worth two minutes to see if it fits what you are dealing with. The link below also takes 10 percent off for you as a reader.
This Week’s Podcast Spotlight
Episode 66: Build Muscle, Increase Strength and Improve Recovery, Blood Flow Restriction Exercise with Dr. Sten Stray-Gundersen
Blood flow restriction training means putting cuffs high on your arms or legs, inflating them enough to slow the blood coming back out, and then lifting something light. A water bottle, a resistance band, your own body weight. The muscle fatigues so fast that a load of 20 to 30 percent of your max starts pulling in the fast twitch fibers you would normally need heavy weight to reach. In one study of older women doing bicep curls, the cuffed group gained as much force as the group lifting heavy. Dr. Sten Stray-Gundersen is an exercise physiologist at the University of South Carolina who has spent more than a decade on hypoxia and exercise, and his father helped design the cuffs we spent two hours talking about. He explained why the growth signal keeps running for 48 to 72 hours after the cuffs come off, why the muscles above the cuff grow too, and how this is one of the few protocols that raises VO2 max and muscle size at the same time. Near the end I handed him four real people and asked him to build each one a program: my parents, my son, my daughter, and me.
Three practical points from Dr. Stray-Gundersen:
- Light weights can do heavy work. With cuffs restricting venous outflow, a load of 20 to 30 percent of your max recruits the same fast twitch fibers that normally require heavy weight. In one trial, older women doing bicep curls matched the heavy load group’s strength gains.
- You need almost no equipment. Body weight squats, glute bridges, wall push ups, and water bottle curls are enough to work with. Muscles above the cuff grow too, so the arms and chest respond even when the cuffs sit at the shoulders.
- Effort matters more than cuff pressure. The target is 3 to 5 sets of 15 to 20 reps where the last few are a real struggle, resting only 30 to 60 seconds. The discomfort should come from the muscle, not from the band digging into your skin.
This Week in Health Science
Five studies from this week’s research, and I think you will find a few of them practically useful.
Cannabis Flattened Brain Development in 11,036 Teenagers
Researchers followed 11,036 American kids from age 9 to 17 and tested them repeatedly. The teens who started using cannabis did not score lower to begin with. If anything they were slightly ahead in late childhood. What changed was the slope: their memory, processing speed, self-control, language, and working memory stopped gaining at the pace their peers kept. That reversal is what makes the finding hard to explain away, because the easy story would be that struggling kids are the ones who use. The hair testing is what lifts this above another self-report study. Almost everything written about teen substance use rests on teenagers telling a researcher what they did, and teenagers under-report. In a subgroup of 645 kids tested between ages 12 and 16, THC-positive hair predicted worse growth in episodic memory, while teens exposed to CBD looked no different from controls. That separation is a real signal, and self-report could never have shown it. This is observational work, so it cannot prove cause. But the honest conversation with a teenager is not about one bad grade, it is about a slower rate of gain across years. The teenage brain is doing its heaviest construction work in exactly the window where cannabis use usually starts, and today’s product is far more potent than what most parents remember.
Key finding: Across 11,036 adolescents followed from ages 9 to 17, starting cannabis flattened growth in every cognitive domain tested (effect sizes 0.11 to 0.52), and in 645 teens with repeat hair testing, THC-positive samples predicted worse episodic memory growth by 0.60 standard deviations.
One Dose of Psilocybin Lifted Depression That Two Drugs Could Not
Sixty adults with depression that had already failed at least two antidepressants took either a single 25 mg dose of psilocybin or a placebo, with preparation sessions before, support during the dosing day, and integration sessions afterward. At week 3 the psilocybin group sat 10.41 points lower on a standard depression scale, and the gap was still there at week 6. The effect size was 1.70, which is the kind of number that makes headlines. The design does not support headline treatment, though. This was a feasibility trial, built to test recruitment and retention, and the depression difference was not the question it was designed to answer. The authors say so themselves. The setting is the encouraging part. This ran inside an NHS clinic rather than a specialized research center, and 59 of 60 people showed up for every follow-up visit. Plenty of promising treatments die because they cannot survive contact with a normal clinic schedule. If you have depression that has not responded to two or more treatments, the legitimate route right now is asking your psychiatrist about trials you might qualify for, and keeping the treatment you are already on.
Key finding: A single 25 mg dose of psilocybin with psychological support lowered MADRS depression scores 10.41 points below placebo at week 3 (95% CI 5.95 to 14.86), sustained through week 6, in 60 adults with treatment-resistant depression.
The MMR Timing Question, Answered in 2.5 Million Children
The question most parents actually ask me is not whether vaccines cause autism. It is softer than that, and it sounds like “could we just wait a few months, to be safe?” That version deserves a real answer rather than a general reassurance, and this study gives one. Researchers pulled 2,560,035 US children from a large electronic health record database and compared autism diagnoses in kids whose first MMR dose fell between 11.5 and 24 months against kids not yet vaccinated at the same age. The risk came out about 3 percent lower, with a range that comfortably includes no change at all. They repeated it at every age band and the answer kept coming back the same. The part I would point to if I had one thing to show a parent is the negative control: they ran the identical method on the pneumococcal booster, a shot nobody suspects, and got the same flat result. Any method can produce a clean-looking answer by accident. Getting the same flat answer on a vaccine no one questions tells you the method is measuring something real rather than manufacturing reassurance.
Key finding: Among 2,560,035 US children, a first MMR dose between 11.5 and 24 months was not linked to autism (adjusted hazard ratio 0.97, 99% CI 0.91 to 1.03), and a negative control analysis of the pneumococcal booster was equally flat (aHR 1.01).
Three in Four Hospital Patients Got an Antibiotic That Wiped Out Their Gut Bacteria
Most of the bacteria in your intestines are anaerobes, and they digest food, train the immune system, and crowd out the organisms that make you sick. Some antibiotics wipe them out as collateral damage. In this sub-study of the BALANCE trial, researchers looked at 2,851 hospital patients with bloodstream infections who had no clinical reason to need anaerobic coverage, and 74 percent of them got a drug that provided it anyway. Those patients had about 41 percent higher odds of dying within 90 days, and stool sequencing showed their gut lost a large share of its anaerobes. Doctors chose the antibiotics here, not a randomization list, so sicker patients may have been steered toward broader drugs in ways no statistical adjustment fully erases. What keeps me from waving it off is the dose response: more days on the drug meant more gut damage and more risk. In the hospital, broad coverage feels like the safe choice, and this says that instinct has a price. It is fair to ask the team whether the antibiotic covers anaerobes, whether that coverage is needed for this particular infection, and whether it can be narrowed once cultures come back.
Key finding: Patients who received anti-anaerobic antibiotics without a clinical indication had about 41 percent higher odds of death at 90 days (odds ratio 1.41, 95% CI 1.03 to 1.92), along with a drop of roughly 16.6 percentage points in the share of the gut occupied by anaerobic bacteria.
High-Dose Vitamin D Did Not Slow Advanced Colon Cancer
A few years ago a smaller phase 2 trial suggested that adding high-dose vitamin D to chemotherapy slowed metastatic colorectal cancer. That is exactly the kind of early signal that deserves a bigger, stricter test, and this is that test. In 455 patients, everyone got the same chemotherapy plus bevacizumab, and the only difference was the vitamin bottle: 8000 IU of D3 daily for two weeks and then 4000 IU, or a standard 400 IU. Cancer stayed under control for a median of 11.8 months on the high dose versus 10.3 months on the standard dose, a gap small enough to be chance. Overall survival, if anything, tilted slightly the other way. I find this useful precisely because the answer is no. A promising result got tested properly and did not survive, and that saves patients from paying for and swallowing something that is not helping. It does not say vitamin D is useless. Correcting a real deficiency for bone and muscle health is a different question with its own evidence. It says that pushing the dose ten times higher on top of full chemotherapy does not buy extra time.
Key finding: In 455 patients with metastatic colorectal cancer, high-dose vitamin D3 gave a median 11.8 months of progression-free survival versus 10.3 months on standard dose (P = .25), with overall survival of 25.6 versus 27.0 months (P = .66).
Stay curious. Stay skeptical. And stay healthy.
Dr Kumar