F. Perry Wilson, MD, MSCE

DISCLOSURES | December 10, 2024

Welcome to Impact Factor, your weekly dose of commentary on a new medical study. I’m Dr F. Perry Wilson from the Yale School of Medicine.

You know those times in your life when you’re just feeling… stressed? You’re on the edge; you have no chill; everything just sort of gets to you. If you can step away from the anxiety for a moment, you might ask yourself where it’s all coming from. Is it really the stuff in your inbox at work or is it money issues at home? Is it something with your relationship, or maybe it’s your sleep quality or your diet? One thing you probably won’t blame for those acute stress reactions is the tonsillectomy you had as a kid. But according to new research, maybe you should. 

Tonsillectomy and adenoidectomy are among the most common surgical procedures young people in the United States undergo, with about 300,000 cases a year, according to recent numbers. That’s down a bit from numbers a decade or so ago, but suffice it to say, a good chunk of the population is walking around right now without their tonsils. 

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The data supporting tonsillectomy have never been great. The two big indications for the surgery are recurrent sore throat — data show that tonsillectomy reduces this by about 0.7 sore throats per year— and obstructive sleep apnea (OSA). The data for improvement of OSA are a bit better than the data for sore throats. 

Also, tonsillectomy is a relatively quick, relatively well-reimbursed surgery with indications that are — let’s be honest — somewhat subjective, and so variation is high. One study found that in a single Vermont town, nearly 60% of the population had had their tonsils removed by the time they turned 18. A few towns over, the rate was 20%. 

A few factors have led to the decline of tonsillectomy in recent years. Reimbursement rates have gone down a bit. Additionally, better data collection and statistical analysis have shown that the benefits of the procedure are relatively modest. 

And then there is a body of medical literature that at first struck me as surprising and almost bizarre: data linking tonsillectomy to subsequent physical and psychiatric disorders. 

I teach a course on interpretation of the medical literature, and one of the first things I teach my students is to check their gut when they see the conclusion of a study. 

Basically, even before you read the data, have a sense in your own mind if the hypothesis seems reasonable. If a paper is going to conclude that smoking leads to increased risk for bone cancer, I’d say that seems like a reasonable thing to study. If a paper purports to show a link between eating poultry and bone cancer, I’m going to be reading it with quite a bit more skepticism. 

The technical term for that process is assessing “biologic plausibility.” If we’re talking tonsils, we have to ask ourselves: Is it plausible that removing someone’s tonsils when they are young should lead to major problems in the future? 

At first blush, it didn’t seem very plausible to me. 

But the truth is, there are quite a few studies out there demonstrating links like this: links between tonsillectomy and irritable bowel syndrome; links between tonsillectomy and cancer; links between tonsillectomy and depression. 

And this week, appearing in JAMA Network Open, is a study linking tonsillectomy with stress disorders. 

Researchers leveraged Sweden’s health database, which contains longitudinal data on basically every person who has lived in Sweden since 1981. This database let them know who had a tonsillectomy or adenoidectomy, and when, and what happened to them later in life. 

I think the best way to present these data is to show you what they found, and then challenge that finding, and then show you what they did in anticipation of the challenges we would have to their findings. It’s a pretty thorough study. 

So, topline results here. The researchers first identified 83,957 individuals who had their tonsils removed. They matched each of them with 10 controls who did not have their tonsils removed but were the same age and sex. 

Over around 30 years of follow-up, those people who had their tonsils removed were 43% more likely to develop a stress-related disorder. Among the specific disorders, the risk for PTSD was substantially higher: 55% higher in the tonsillectomy group.

That’s pretty surprising, but I bet you already want to push back against this. Sure, the control group was the same age and sex, but other factors might be different between the two groups. You’d be right to think so. People who got their tonsils out were more likely to have parents with a history of stress-related disorders and who had lower educational attainment. But the primary results were adjusted for those factors. 

There’s more to a family than parental educational attainment, of course. To account for household factors that might be harder to measure, the researchers created a second control group, this one comprising the siblings of people who had their tonsils removed but who hadn’t themselves had their tonsils removed. 

The relationship between tonsillectomy and stress disorders in this population was not quite as robust but still present: a 34% increase in any stress disorder and a 41% increase in the risk for PTSD.

Maybe kids who get their tonsils out are just followed more closely thereafter, so doctors might notice a stress disorder and document it in the medical record; whereas with other kids it might go unnoticed. This is known as ascertainment bias. The researchers addressed this in a sensitivity analysis where they excluded new diagnoses of stress disorders that occurred in the first 3 years after tonsillectomy. The results were largely unchanged. 

So how do we explain these data? We observe a correlation between tonsillectomy in youth and stress disorders in later life. But correlation is not causation. One possibility, perhaps even the most likely possibility, is that tonsillectomy is a marker of some other problem. Maybe these kids are more prone to infections and are therefore more likely to need their tonsils removed. Then, after a lifetime of more infections than average, their stress responses are higher. Or maybe kids with a higher BMI are more likely to have their tonsils removed due to sleep apnea concerns, and it’s that elevated BMI that leads to higher stress in later life. 

Or maybe this is causal. Maybe there actually is biological plausibility here. The authors suggest that removal of tonsils might lead to broader changes in the immune system; after all, tonsillar tissue is on the front line of our defense against pathogens that might enter our bodies through our mouths or noses. Immunologic changes lead to greater inflammation over time, and there is decent evidence to link chronic inflammation to a variety of physical and psychological disorders. 

In support of this, the authors show that the kids with tonsillectomy were more likely to be hospitalized for an infectious disease in the future as well, in magnitudes similar to the increased risk for stress. But they don’t actually show that the relationship between tonsillectomy and stress is mediated by that increased risk for infectious disease. 

In the end, I find these data really intriguing. Before I dug into the literature, it seemed highly unlikely that removal of these small lumps of tissue would have much of an effect on anything. Now I’m not so sure. A few things can be removed from the human body without any consequences, but it can be hard to know exactly what those consequences are. 

That said, given the rather marginal benefits of tonsillectomy and the growing number of studies expanding on the risks, I expect that we’ll see the rates of the surgery decline even further in the future. 

F. Perry Wilson, MD, MSCE, is an associate professor of medicine and public health and director of Yale’s Clinical and Translational Research Accelerator. His science communication work can be found in the Huffington Post, on NPR, and here on Medscape. He posts at @fperrywilsonand his book, How Medicine Works and When It Doesn’t, is available now. 

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