Neurobiology of Setting Healthy Boundaries

Jun 30, 2025

Hey Rewire Collective!

Welcome to this week’s newsletter! We’re diving into the neurobiology of setting health boundaries and why it’s good for your brain.

And if you missed it, I’ve got a YouTube video explaining it too:

Boundaries; What are They?

Our brains are wired to respond to our environment. Typically, it’s the amygdala that runs the show on our emotional responses (think fight-or-flight), unless the prefrontal cortex steps in to keep us calm and respond rationally. However, the more ‘threatening’ a situation, the more pressure the amygdala asserts. And the more the amygdala runs the show, creating spirals of anxiety and stress, the more the amygdala WILL run the show in future scenarios. Remember, neurons that fire together, wire together – the more we practise a behaviour, even inadvertently, the more likely it becomes we’ll act that way in the future.

Boundaries are a great way to create space to allow the prefrontal cortex to jump in and calm things down before the amygdala overreacts. Boundaries make it less likely for your amygdala to activate because they reduce the likelihood of stressful things happening, and give you time to react when they do. You can think of boundaries like fences surrounding you: they’re there to protect your emotional and mental well-being. They keep people at a distance from you to create that space for the prefrontal cortex. The fences will have gates to let some people in, but you can be more or less selective, with more or fewer gates, depending on your needs.

Healthy boundaries look like (1, 2):

Confident saying ‘no’ when something doesn’t align with your values.
Feeling confident in your own opinions and values.
Being able to separate yourself from others' problems, not absorbing their emotions.
Not accepting abuse or disrespect.
Feeling comfortable when someone else says ‘no’ to you.

Boundaries can have too many gates (letting too many people in) or too few gates (letting no one in). Someone who says no to everything and therefore never creates intimate and personal relationships is not setting healthy boundaries. Similarly, someone who depends heavily on others' opinions and cannot say no to any request does not have healthy boundaries.

Boundaries can also be different in different contexts: you might have rigid boundaries at work and more porous boundaries with family.

Why are boundaries tricky?

They’re counterintuitive to our evolutionary instinct that wants to be social. Often, setting a boundary means saying no to someone, or reducing the amount we see a person. This goes against our social nature that depends on connections with others. So if you find it tricky to put boundaries in place, you’re not alone, and it’s not your fault.

An aside, but if you grew up in a narcissistic household or with emotionally dependent caregivers, boundaries were definitely a no-no, which reinforces this fear of social rejection that may come when setting a boundary. It will likely be harder for you to learn how to put boundaries in place, but NOT impossible!

The funny thing is that research shows that setting boundaries benefits our relationships and our overall life satisfaction.

A study from the Netherlands showed that employees with blurred work-life boundaries were more likely to be unhappy because of emotional exhaustion (3).
A study on postdoctoral researchers showed that boundary control is associated with greater life balance which was associated with less anxiety and depression (4).

Why do boundaries work?

Remember, the goal with our boundaries is to keep the amygdala calm, and keep the prefrontal cortex in control (5). Boundary setting is really just allowing us to regulate our emotions. And the more we practise, the better we get.

The same brain systems involved in emotional regulation are also activated during boundary-setting, and boundary-setting helps strengthen our ability to emotionally regulate. Created in https://BioRender.com

Methods that help us to emotionally regulate, including cognitive reappraisal (6,7,8) (which helps us re-assess the situation logically), increase the activity of the prefrontal cortex and decreases the activity of the amygdala. This is extremely effective in people with anxiety and depression (9).

Interestingly, neurofeedback training shows that we can do this ourselves, regulating our amygdala activity and increasing control of our prefrontal cortex by thinking about positive memories in stressful situations (10,11) . This is particularly useful in people with borderline personality disorder. It’s an effortful process, but practice makes perfect.

And we see from larger brain imaging studies that strengthening the connection between the prefrontal cortex and amygdala, such that amygdala activation is lessened, changes the way we respond to stress (12). It changes our behavioural response, less anxiety and emotion, but also our physiological response, producing less stress hormone and a lower heart rate.

If you have a friend who stresses you out because all they do is talk about negative things, you can take steps to set up healthy boundaries, like limiting the amount of time you see them for, inserting positive stories into the conversation, and also openly saying ‘I don’t have the emotional capacity to carry this today’.

When we set personal boundaries, like refusing to respond to work emails after hours, we’re activating the same brain systems involved in emotional regulation. The prefrontal cortex takes over, keeping us close to our core values (‘I deserve rest’) and then suppresses the amygdala-driven stress response.

Top Tips

If your amygdala has already become triggered and you’re spiralling into worst-case scenario, try writing out what’s going on, or writing a pros and cons list. The act of writing will help your brain shift out of emotional panic and into logical thinking.
You have to practice allowing your prefrontal cortex take over.
It’s easier for your prefrontal cortex to take over if the amygdala isn’t as active. Practices like meditation and mindfulness can help calm the amygdala.
If you’re trying to implement a boundary with people, practise what you’re going to say in advance. Use visualisation to imagine how you would say it, and practise standing your ground.
Emotional regulation is a large part of boundary setting. Trying other techniques like CBT, Cognitive Reappraisal, and Neurofeedback Training which also help with emotional regulation will be a great addition to setting healthy boundaries.

Until Next Week,

Nicole x

P.S. Leave a comment with topics you want discussed in future newsletters!

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