How Inflammation Changes Our Thinking

Nathan Cowley/Pexels

In the last several decades, we’ve increasingly understood that chronic inflammation plays a major negative role in our health, contributing to the risk of developing diseases like diabetes, hypertension, and dementia.

More recently, research has revealed that the effects of inflammation reach much deeper into our physiology. Mounting data have demonstrated that inflammation changes the way we think, altering our mood and even our decision-making. This powerful information has significant implications for both individual and public health.

The idea that inflammation affects our brains and our thinking is not all that novel. Higher levels of inflammation are commonly seen in illness, and it’s well known that sickness is associated with thinking problems. For example, up to 80% of critically ill patients requiring ICU care in a hospital develop delirium, a condition described as the new development of confusion or otherwise altered mental status. And though many factors contribute to delirium, it’s now thought that the sickness-related inflammatory response in the brain drives some of these cognitive changes.

Of course, it’s one thing for hospitalized patients to show changes in their thinking; they’re very sick, and they’re also in a stressful foreign environment. But think back to the last time you had the flu or a cold. Chances are, you didn’t feel your brain was at its best. In fact, research has shown this to be accurate.

In a 2012 study, researchers tested sick and healthy people’s decision-making on a driving simulator and found that sick participants demonstrated significantly slower reaction time. This is in line with prior research showing that just feeling ill is associated with slowed memory and worsened mood.

So, our memory, reaction time, and mental health all appear to suffer when we’re ill and have higher levels of inflammation. In fact, when it comes to mood, the scientific connection between inflammation and depression has become quite robust.

To start, multiple studies have demonstrated that people with depression show significantly elevated levels of inflammation in their blood. More to the point, volunteers injected with chemicals that induce inflammation demonstrate increased symptoms of depression just a few hours later, indicating that inflammation may actually cause depressive symptoms. Despite these concerning data, the latest research on inflammation ups the stakes even further because it implicates the actual decision-making process.

It’s clear the ability to make good, long-term oriented decisions is imperative for our well-being. It’s what keeps us from spending all our money on a whim, from yelling at our boss, and from eating junk food at every meal. On the other hand, when we engage in impulsive, quick-fix solutions, the results can be catastrophic. That’s why it’s both illuminating and frightening to see that higher levels of blood inflammation predict decisions characterized by impulsivity and an inability to delay gratification. In another study, when researchers induced inflammation in volunteers, they found that these elevated levels of inflammation also predicted more impulsive thinking.

Inflammation then, may lead us to respond to the world in a more reactive, impatient manner. This may help explain why depression (again, a disease strongly tied to elevated levels of inflammation) is associated with more impulsive thinking. Obesity, another inflammatory condition, has been connected with less future-orientation, but recent evidence suggests higher levels of inflammation in the blood may be responsible for this finding as well.

Considering the global burden of depression and the personal and societal costs associated with impulsive thinking, interventions to dampen inflammation in our bodies and brains must become a priority. To this end, we can consider the need for diets low in refined carbohydrates and added sugars, stress management techniques, and regular exercise as key components of a lifestyle geared for better mood and better decisions.




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Austin Perlmutter, MD

Austin Perlmutter, MD

Dr. Austin Perlmutter, co-author of BRAIN WASH, is a board-certified internal medicine physician.

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