Depression is a mood disorder characterized by persistent sadness, loss of interest or pleasure, and disruptions in thinking, energy, or daily functioning that interfere with one’s ability to carry out daily activities. For years, depression was widely believed to result primarily from a “chemical imbalance” related to serotonin. However, a major umbrella review in the early 2020s found no consistent evidence that low serotonin levels cause depression—helping explain why many patients experience limited improvement from selective serotonin reuptake inhibitors (SSRIs) or serotonin–norepinephrine reuptake inhibitors (SNRIs). As a result, researchers have shifted toward a broader understanding of depression, including the possibility that chronic inflammation—particularly in the brain—may play a meaningful role.

Although this link between inflammation and depression may sound new, it’s actually well established in scientific literature. A meta-analysis of 38 studies involving more than 58,000 participants sought to clarify the direction of this relationship. The authors found that elevated levels of the pro-inflammatory cytokine IL-6 and the inflammatory marker C-reactive protein (CRP) predicted a higher risk of developing depression later on—and the higher these levels were, the more severe the depressive symptoms tended to be. Current evidence suggests that inflammatory signals can influence the brain by disrupting neurotransmitter function, stress-response pathways, and neuroplasticity, all of which contribute to mood regulation. Still, researchers continue working to determine exactly how much a role inflammation plays in overall depression risk and which individuals are most affected.

Growing evidence also suggests that people with depression (or at risk for it) may benefit from lifestyle habits known to reduce systemic inflammation. These include regular exercise, maintaining a healthy weight, reducing sedentary time, limiting screen time, getting quality sleep, spending time outdoors, eating an anti-inflammatory diet, managing stress, limiting alcohol intake, and not smoking. In fact, a 2024 study reported that individuals with the healthiest, lowest-inflammation lifestyles had up to a 55% lower risk of depression compared to those with the unhealthiest lifestyles.

These findings are encouraging, especially given current trends. According to recent Centers of Disease Control and Prevention and Gallup data, nearly one-third of Americans will experience an episode of clinical depression at some point in their lives, and about 17% report symptoms at any given time—a rate nearly double what was seen a decade ago. While these statistics are concerning, they also highlight the importance of addressing the factors that can reduce risk. And if pain or stiffness is keeping you from exercising or adopting healthier routines, consider seeing your chiropractor. Sometimes just a handful of visits can make it easier to move comfortably and stay active.