Psychological and behavioral interventions change the way the nervous system, endocrine system, and immune system interact with each other.

We analyzed the available evidence and found that 73 studies or assertions suggest psychological and behavioral interventions can change how the nervous system, endocrine system, and immune system communicate with each other [1]. There are no studies in our review that contradict this. These systems work together to help the body respond to stress, illness, and daily challenges. The nervous system sends signals, the endocrine system releases hormones like cortisol, and the immune system defends against threats. Psychological interventions—like mindfulness, cognitive behavioral therapy, or stress management training—and behavioral changes—such as improved sleep or regular physical activity—appear to influence this network. What we’ve found so far indicates these approaches may shift how these systems talk to one another, potentially reducing overactive stress responses or improving immune coordination. The evidence we’ve reviewed leans toward the idea that how we think, feel, and behave can affect biological pathways that were once thought to be separate or fixed. For example, learning to manage stress might lower cortisol levels and reduce inflammation markers over time. But we don’t yet know exactly how strong or lasting these changes are across different people or conditions. We haven’t seen any data showing these interventions have no effect, but we also haven’t seen enough detail to say whether all types of interventions work the same way, or for everyone. The number of supporting reports is high, but the quality, duration, and measurement methods across these studies vary. What this means for everyday life: if you’re working on reducing stress, improving sleep, or building healthier habits, it’s possible you’re not just feeling better mentally—you might also be helping your body’s internal systems communicate more effectively. Keep going. The science we’ve reviewed so far supports that effort.