Stress is where everything converges, and where a lot can change.

Heart. Thirteen European studies pooled the records of nearly 200,000 working adults and followed them for about seven years. Those who reported job strain, meaning high demands with little control, had a 23% higher rate of first heart attacks, after accounting for smoking, weight, and the usual risk factors (Kivimäki, Lancet 2012). The effect is real and smaller than smoking or sitting still. Stress is one risk factor among several, which is also why it responds to the same kind of care.

Immunity. Cortisol is the hormone that is supposed to turn inflammation off once it has done its job. Sheldon Cohen's group at Carnegie Mellon interviewed 276 healthy adults about long-running stress in their lives, then exposed them to a cold virus under quarantine. The people under chronic stress had immune cells that no longer responded to cortisol, and they were the ones who caught the cold. Inflammation that will not switch off sits underneath heart disease, diabetes, and autoimmune flares (Cohen, PNAS 2012).

Autoimmune disease. A Swedish registry study followed 106,000 people diagnosed with a stress-related disorder for about ten years and compared them with a million matched controls and with their own siblings. They developed autoimmune disease at a 36% higher rate, and the sibling comparison held, which argues against family background as the explanation (Song, JAMA 2018). This is observational. It says that stress severe enough to need a diagnosis is followed by more autoimmune disease. It does not say that ordinary daily stress does the same, and no one has shown that yet.

Reversal. In the Lifestyle Heart Trial, people with blocked coronary arteries who changed their diet and exercise also spent an hour a day on stress management: stretching, breathing, meditation, and relaxation. Their arteries began to open within a year while the control group's kept narrowing (Ornish, Lancet 1990). The trial cannot separate the stress work from the rest of the program.

What helps. Johns Hopkins researchers reviewed 47 randomized trials of meditation programs with 3,500 participants. Mindfulness practice gave small to moderate relief of anxiety, depression, and pain, in the same range as antidepressants in some trials, with no side effects. It was no better than exercise, relaxation training, or talk therapy (Goyal, JAMA Intern Med 2014). The lesson I take from that is that the particular method matters less than doing something every day.