Cortisol

These are synthetic drugs given deliberately to ripen a baby's lungs, which is a different matter from living with a lot of one's own cortisol. What becomes of those children years later is still being studied. So is the safety of giving more than one course.

Most of the pooled studies took a single snapshot rather than following anyone, so nothing here shows stress moving the surge. The stress measures themselves are a mixed bag, from job strain to burnout, and they do not all point the same way, which is the finding rather than a flaw in it.

Every study pooled here watched people rather than assigning anything, so a flat curve may mark illness already underway rather than cause it. The slope was measured differently from study to study, from two saliva samples a day to six or more, which blurs the pooled figure.

This only tracks a pattern over time, so it cannot show cause. Just 32 of the deaths were from heart disease, which makes the estimate rough. Cortisol was measured on one ordinary weekday. Morning cortisol on its own showed no link at all.

The mechanism is shown far more directly in the animal studies than in the human ones, where nobody has followed it over time. And this is about how cells respond rather than how much hormone is present, so a blood cortisol reading says nothing about whether it is happening.

Thirty-four people finished the trial, but the treatment effects were computed on 26 — the ones who had actually reacted to the task at baseline, picked out after the fact. An industry grant funded the study, and the paper says the funder had no hand in the analysis. The other ingredients were phosphatidylserine, alpha-glycerylphosphorylcholine and chamomile, each in a small dose. Why the two effects arrived two hours apart is unexplained. Performance on the task itself never moved.

Thirty-six people enrolled and 34 finished, but the effects were computed on 26, chosen after testing and before unblinding for having reacted to the task at baseline. Four people gave too little saliva and were left out of the cortisol analysis, and the paper does not say how many remained. The drink was not theanine alone: it also carried 25 mg of alpha-glycerylphosphorylcholine, 1 mg of phosphatidylserine and 10 mg of chamomile. Before dosing and at one hour the task did not reliably raise cortisol, so the rise the drink blunted appeared at one session out of three. A grant from a company, Neurobrands, paid for the trial, and the paper says the funder had no input into its design, conduct or interpretation.

Twenty-six of the 34 who finished were analysed, and they were the ones who had reacted to the task at baseline. The drink was not theanine alone: phosphatidylserine, alpha-glycerylphosphorylcholine and chamomile came with it, in small doses. An industry grant funded the trial, and the paper says the funder had no hand in its design or analysis. A brain-wave finding in the same trial turned up only in the more anxious participants and did not track the stress or cortisol results, so it stands unexplained.

Forty people took the dose, and each took it once, so this shows what one sharp rise does rather than what months of raised cortisol do. The loss was confined to recalling facts and handling space, which leaves much of what memory does unaffected.

The group was small and elderly, and the published summary never says how many people were in it. In humans this is a correlation; the evidence that cortisol itself damages the structure comes from the rat work the same paper cites. Ageing or illness could equally shrink that structure and raise cortisol at once, which would draw this same pattern with no link between them.

One hospital, 250 people. Facing major surgery can itself distort cortisol patterns, so this may not reflect ordinary life. A flatter drop may also mark someone who is already sicker, rather than adding risk of its own.

This is a narrative review drawing human and animal work together, not new data. And the arrow could run either way: a stress-disrupted cortisol system might raise autoimmune risk, or years of autoimmune illness might be what disrupts the system. Nothing here separates the two.

The authors describe the effects as small. Everyone measured was young and healthy, at an average age of 20, so this says nothing about older adults or about anyone with a sleep or stress disorder. And these are the same people watched over time rather than an experiment, so something else in their days could be driving both ends.

These were tiny experiments, 13 men in one of them, run over one or two nights. All the participants were young men, so nothing here covers women or older adults. And a night or two of lost sleep is not years of it, so how far the flattening goes over a lifetime is unmeasured.