The Science Behind Mood Swings – What Every Woman Should Know

Dec 22, 2018

Dr. Ashley Margeson

Dr. Ashley Margeson



Ah, mood swings. These events are often tsunami-like rapid and extreme fluctuations in our emotional state where we go from feeling happy and ecstatic to crying at the latest Tim Horton’s commercial or feeling like we’re ready to commit murder. 

Maybe it’s not always that extreme, but mood swings can seriously mess with our days. 

Among the possible causes of mood swings is a fluctuation in the brain chemicals associated with regulating our mood.

These brain chemicals are supposed to change throughout the day in response to our environment, our hormones and even our mental wellbeing; but a combination of sensitivity and stability are what make some women very sensitive to mood swings, and others not-so-much. 

So let me start with my usual acknowledgement that we don’t actually know a lot about PMS, mood swings or why some women experience it, and others don’t. So I’m pulling together some of the research that we do have, but I want you to know that the story is FAR from complete. 

Among the brain chemicals that we have fluctuating about, the hormones estrogen and progesterone are also at play. These two hormones are known as neurosteroids (1), which means they act as stimulants on our brain and help regulate mood and memory. These shifting levels of our hormones affect our brains and nervous system differently throughout our cycles; affecting our behaviour, our emotions and even our thoughts. 

Estrogen alone can improve your mood and wellbeing, but progesterone can sometimes have the opposite effect (2). Both estrogen and progesterone together can disrupt brain chemicals that need to be able to communicate well; serotonin and GABA (gamma-Aminobutyric-Acid) (3). A lower amount of progesterone relative to estrogen in the second half of your cycle can disrupt how serotonin is able to communicate with GABA; which can lead to depression, fatigue, some serious food cravings and difficulty sleeping (4). But a lower amount of progesterone relative to estrogen in the first half of your cycle actually helps to keep things stable. Confusing, eh? 

The thing is, GABA is your calming neurotransmitter; and one of the by-products of progesterone (the beta form – alloprenanolone) actually stimulates the GABA receptors in your brain. This helps calm you down (5), and regulate your stress, anxiety and alterness; providing your ratio of progesterone and estrogen are balanced in your body. An imbalance of those hormones can definitely cause those pre-period mood swings to be more extreme because the serotonin and GABA receptors don’t get the simulation the way that they should due to a decrease in bioavailable progesterone and alloprenanolone. 




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