A Man's Brain on Fatherhood

As a specialist in child and adolescent psychiatry, and the founder of Canada’s first Fathers’ Mental Health Clinic, I’ve been working with dads’ brains since 2012. Fast forward to 2026 and I recently discovered PhD psychologist Darby Saxbe and her new book, Dad Brain: The New Science of Fatherhood and How It Shapes Men’s Lives. The book validates what I have witnessed, provides rich science for new concepts and theories, and inspires new ideas to support fathers and families. I would encourage you to read the book as well as listen to podcast interviews with Dr. Saxbe, which brings her words and concepts to life. I look forward to highlighting the intersections of her book and my clinical work below, and in a series of upcoming posts.

What happens to our brain when our life is disrupted and transformed by parenthood?

Figure 1. Our brain and it's functions

First and foremost, the book asks the fundamental question, “What happens to our brain when our life is disrupted and transformed by parenthood?”

Simply put, the brain has 3 core functions: thinking, feeling and behaving. (Figure 1). Networks in our brain connect our thoughts, emotions and our actions. Cognitive Behavioural Therapy implies that if we change our thoughts or our behaviours, we can change how we feel. For example, I have used Behavioural Therapy with a focus on behavioural change, to effectively treat postpartum depression in dads as well as moms, in one of the world’s largest psychotherapy randomized controlled trials ever conducted.  Inside this triangle of thoughts, feelings and behaviour, is what I call, Brain Biology. Brain Biology includes brain structures and circuitry (such as the prefrontal cortex and neural networks), chemistry (neurotransmitters like dopamine, neuropeptides like endorphins, as well as medication and substances), and physical states such as sleep, stress, exercise and illness. Changes in brain biology can affect the way we think, feel and behave. Changing our thoughts, emotions or behaviours can also affect our brain biology!

Figure 2. Brains are affected by their environment

Our brains also interact with the information we sense from the world around us. The safety of our environment and the health of our relationships will also affect our brain biology and how it functions. (Figure 2)

Our brains grow through a series of developmental milestones and life events, creating memories and learning along the way. Brain biology initiates and facilitates some of this growth, such as producing hormones to stimulate the onset of puberty. Our environment will also influence our personal growth and contribute to when and what we will learn. Some people refer to this as nature and nurture, and together our inner and outer worlds interact resulting in how we think, feel and act in any given moment. I like to think of brain development as my favourite chocolate bar, Toblerone, a series of life events and milestones in the form of connecting pyramids (Figure 3).

Figure 3. Brain development over time through several moments of connected thoughts, feelings and behaviours

Dr. Saxbe has been studying changes in the brain’s structures as adults transition into parenthood. Changes in the brain’s anatomy, such as thinning of the prefrontal cortex (reduced grey matter), are

thought to represent learning, specialization and improved connectivity in the function of that area of the brain. Both moms and dads have undergone brain imaging before and after the birth of their child, to determine whether or not, becoming a parent changes the anatomy of the brain.

Becoming a Parent is a Massive Learning Event

Becoming a parent is a massive learning event for either parent, with some parents learning more than others. Learning how to parent can occur through reading, reflecting, and doing. In addition to hormonal changes, sleep deprivation, reduced exercise, and increased consumption of uneaten baby snacks, the brain is also affected by engaging in a whole new relationship. I would argue that there are two new relationships after the birth of a child. The first one is obvious, you and your child. The second one is the new relationship with your spouse, as co-parents. This is a different relationship than the one you would describe as partners or lovers. Navigating these adult relationships can be challenging and rewarding - more to say on that in a separate post. 

"Action leads to confidence, don't wait for confidence before acting"

The father-child relationship is, of course, very new. Learning as a parent is not just about learning new tasks like how to feed and swaddle an infant, change a diaper, or prepare baby food; it is also about watching their face, responding to their cries and cues, reading their mind, and putting into words what they see and feel. This learning even extends to when we are away from our child, when we think about our worries and hopes, as well as all the planning and preparation in between activities. Some refer to these latter aspects of parenting as the cognitive load or invisible labour; which is more commonly held by mothers, but fathers are capable of carrying their own load too. This father-child relationship builds the “mentalizing muscle” in our brain, and like any muscle, it gets stronger and better with practice. The more time we spend with our child the more likely we are going to understand their internal world (thoughts and feelings) and predict how they might engage (behaviours) with the environment around them. Mentalizing another person is not unique to parent-child dyads, we can experience this with our partner or anyone, the better we get to know them. Experiencing mentalization is a fundamental component of building a healthy attachment and having a healthy attachment with our child is a significant indicator of future good health for both of us. 

New Mentalization = Changes in the Brain

Scientists have been able to identify the region and network of the brain most associated with our mentalizing capabilities, so it is no surprise to learn that Dr. Saxbe has discovered important and positive changes in this area of the brain in new parents, both mothers and fathers. The change does appear to be “dose dependent” for fathers and that the more time fathers spend with their child, the more likely they are to show changes in this area of the brain, from pre to post childbirth. 

"Father's adaptation to parenthood, is an example of an experience dependent neuroplasticity" [Re:Thinking Podcast with Adam Grant and Darby Saxbe - June 15, 2026]

One way to put this all together for fathers, using our triangle model, is that our environment changes with the birth of our child. This results in feeling anxious, fearful, uncertain as well as joy, hope and love. We might have thoughts about ourselves that range anywhere from  “I don’t know what I am doing” to “I’ve got this”. Our emotions and thoughts are likely going to inform our behaviour and how far we step into or step away from parenting our child. The more we step into it (behaviour), the more likely our confidence (thoughts) and comfort (emotions) with parenting is going to improve and the more we are going to learn about our child, and quite possibly ourselves. As we learn to mentalize our child’s feelings, we may also learn more about our own inner world (as well as that of our partner’s). Dr. Saxbe’s lab confirms that fatherhood changes our brain, and from personal and professional experience, I agree.

Perhaps what is most significant, is how fatherhood affects the brain of our children. One can only imagine the impact on our child’s brain biology, emotions, thoughts and behaviours when their engaged father sits inside their environment.

How as Your Brain Changed During Fatherhood?

To learn more about other related changes that occur in fatherhood, such as testosterone levels, stay tuned. In the meantime, think about how your brain has changed since you entered fatherhood. Ask yourself these questions:

1. How did my brain biology change within the year after my child was born? (e.g. Did I sleep or exercise less, start a new medication, change my alcohol consumption)

2. What were my common and recurring thoughts during my transition to parenthood? (including the ones I kept to myself)

3. How was I feeling as a new father? (list all the emotions, no judgement)

4. What aspects of parenting did I step into and step away from?

5. How did the changes in my brain as a father affect how I experienced the world in other relationships or at work?