Do you remember Biology class? Probably not much of it, but one statement likely sticks out in your memory: Mitochondria is the powerhouse of the cell.

It’s likely that you remember this statement to be important enough that your teacher drilled this idea into your brain.

Well there might be a bit more to this generalized statement of Biology. What if I told you that how you feel and think and deal with stress actually involves the mitochondria?

Before going into that, let’s refresh our memories about what exactly “the powerhouse of the cell” generally means for the Mitochondria.

Our body is made up of trillions of cells! Cells are the Lego pieces that fit together to create the structure that forms us as humans. In cells, there are different subunits that help the cell called organelles. These tiny parts of cells each have a specific function. Mitochondria are one of those organelles– and I am sure you might have an initial guess about what they do!

These small but mighty organelles are organized by the different regions created by their two membranes – the outer and inner membranes. These membranes are boundaries that keep together parts of the mitochondria and determine what can enter into the mitochondria. The outer membrane is focused on housing proteins and enzymes, the pieces that provide structure, regulate processes, and transport materials throughout the cell. The inner membrane, which includes the cristae (the folds) and the matrix (the space), include space for chemical reactions, production of ATP (energy), and mitochondrial DNA (genetic information).

We call these little organelles the powerhouse because of one of its central functions: energy production. Think of where you would be without energy: on your bed, lazily watching Netflix? Yes – in the colloquial sense. But, without your mitochondria’s energy production, your cells are not going to function to keep you alive.

Mitochondria are like windmills that convert energy into power for the farmhouses; they break down sugar into energy, and this useable energy is utilized by all the other important cells to make our bodies function.

You might now be asking if mitochondria are the source of physical energy, what do they have to do with a Psychological Powerhouse? Well, while Biology, Neuroscience, and Psychology have always been friendly, these fields are often afraid to interact too much. A lot of factors contribute to this disconnect between the fields, but it is important to understand this broader interaction to understand that how we function as humans physically impacts us mentally.

When we take a step back and examine a larger picture, we find that this powerhouse organelle, whose main focus is energy production, actually has a very interesting relationship with psychological stress.

The mitochondria’s functions extend far past energy production.  In the course of producing energy, mitochondria have the ability to sense stress mediators, such as its ability to sense environmental, metabolic, and neuroendocrine stressors, whether they are a lack of nutrients or particular hormones. Picard & McEwen (2018) explored this relationship between psychological stress and mitochondria.

When a stressor occurs, there is an effect on the way mitochondria interact with each other and undergo morphological and function changes. Think of how the way you and your Uncle interact differently at a funeral. You dress, talk to each other, and hug differently than when you normally see her on a regular basis because you are in a different and stressful environment; mitochondria also look and act different with each other when undergoing stress.

In the short-term these types of changes may result in adaptation, but in the long term, stressors can result in chronic alterations within the mitochondria (Picard et al., 2015).

When multiple stressors cumulate to the dysregulation of the immune system in the body, allostatic load occurs, and it contributes to long-term effects on the body – both physically and mentally.

What exactly is an allostatic load? Have you ever started to make a pile of semi-clean clothes on that one particular chair in your room? They are dirty enough not to make it into your dresser, but clean enough that you don’t need to put them in the laundry. Allostatic load is when that pile eventually gets so high over time that it becomes too heavy to physically carry and you mentally cannot determine how to fix the pile as it is overwhelming; the clothes are the different types of stress that pile up metaphorically in your body, physically and mentally. This concept can occur in the mitochondria as well.

When the mitochondria sense the stress mediators (such as increases in the stress hormones cortisol and catecholamine), changes occur to its structure and functions. Over time, these constant changes damage the mitochondrial DNA that is stored in the organelle and diminish its capacity for energy production. Thus, the important systematic processes that are in connection with the mitochondria are negatively influenced, meaning that your body’s cells are no longer recieving all the energy they need. This effect of chronic stress on mitochondria is termed mitochondrial allostatic load (MAL).

Think how if you kept attending those funerals as well as had other stressful events, you would feel physically and emotionally drained from all the changes in behavior you have when interacting with other people. Your relationships would be negatively affected by your lack of energy and mood changes from the cumulation of stressful events.

Just like this cumulation from stress would have many negative consequences for your life, chronic stressors have many negative affects to mitochondria because of MAL.

MAL can result in cellular dysfunction, which can lead to health effects like high blood pressure, cardiovascular disease, diabetes, cognitive issues, among others.

MAL can also impact brain structure and function, such that areas of the brain like the hippocampus (responsible for explicit memory) and the medial prefrontal cortex (responsible for decision-making) are atrophied (shrinking quality).

Overall, it is apparent through this framework of MAL, that our favorite powerhouse of the cell is also a psychological powerhouse – one that has interactions with psychological stressors and impacts our brain as well as our physiological functioning.