Thursday, February 23, 2017

The brain's alarm clock and lullaby song - cortisol and melatonin.

How did you wake up this morning? It is a Thursday to me, and fortunately I have my five year-old (biological alarm clock) who still wakes up very reliably between 6:20-6:45 every morning. He has a very stabilized circadian rhythm, or circadian clock. Had he not awoken me, my alarm was set to go for 7:00. Would I have waken up at 7:00 without an alarm? So how does our sleep cycle work with the help of two hormones, and what can we do to get a good balance between those two hormones, cortisol and melatonin? I hope to look into a number of questions regarding sleep and our brain, and discuss two key hormones in this post. Let's start by looking at a typical daily graph of these two hormones:

As we can see in the graph above, when comparing the two hormones, melatonin appears to rise and fall at a sharp rate, whereas cortisol seems to escalate and then drop off more gradually. This can be seen very easily in individuals who have a very rhythmic pattern of sleeping. Not to pick on him, but my son rarely steps outside of the 19:30 - 20:00 window to fall asleep, and as a result, has 6:20-6:45 very consistently as a time to wake up. He likely has a very consistent graph that would look something like that above. Unfortunately, as we leave childhood, many of us, for a myriad of reasons, seem to allow our circadian rhythm to become far less predictable and consistent.

There are many ways by which we (notably starting as teens, and continuing into adulthood) can modify these levels which can ultimately result in less efficient means of sleeping:

  • Screen light (notably the blue light) suppresses the release of melatonin. Therefore, if given the the choice of reading off something digital vs. something printed (or emulates being printed and requires a backlight--Kindle, etc.) you are far better to go with the latter to ensure release of melatonin. 
  • Consolidation of memories is something that is key to retaining memories. Note the time in the graph above from about 11 pm to 3 am where the melatonin is very high--this is needed for us to allow the hippocampus to move our memories into our long-term memory. If you have seen the movie Inside Out, this is the stage where all memories are moved out of the main control centre into the storage area; that is a perfect analogy. (If you haven't seen Inside Out, and you have any remove interest in neurology, you need to watch it--it is brilliant.)
  • The circadian rhythm in teenagers is typically atypical; it does not look like the textbook example above at all. Teenagers are authentically feeling groggy and able to stay up late as things that are currently high in their blood, such as the growth hormone, can affect both cortisol and melatonin. 
  • In this earlier post I discussed some negative effects seen in children who watch excessive amounts of TV. When we break this down into really watching television programming vs. playing video games, video games can result in a much greater alteration to these hormone levels. Not only does the screen light suppress melatonin, but the action of playing a video game can release large amounts of cortisol. Research has shown that between all categories of video games, first-person shooters ultimately release the greatest amount of cortisol. Ultimately, regardless of the genre of the video game, playing video games late at night is reversing the direction both of those hormones are wanting to go to assist one in falling asleep.
  • Our high level of cortisol in the morning can be seen as being quite helpful for the handling of anxiety and stress. Cortisol ultimately promotes the use of all parts of our brain, while fatigue (low cortisol) can often have us stepping away from using areas of our brain key to decision-making such as the PFC. People deciding to stay up late may not be able to have it as high the next morning; this results in one unable to handle the same level of stress and anxiety as one who had a good night's rest.
  • Wanting to move towards really having a consistent circadian rhythm? Make your schedule for weeknights very concrete. While life can often be complicated, if you can ultimately make the amount of screen-time in the evening limited, and place physical exercise as a consistent part of your daily routine, you will likely find your circadian rhythm becoming more like the textbook example above.
  • Drink coffee or tea in the morning to wake up? The chemical caffeine isn't what really raises your alertness, the caffeine releases mycotoxins, which ultimately lead to the release of cortisol, which then wakes us up. 
  • Drink wine or beer in the evening to go to sleep? Alcohol leads to drowsiness as a result of an increase in production of melatonin. Any significant amount of alcohol can result in higher-than-normal levels of melatonin in the morning, resulting in a groggy feeling the following day.
  • In many countries, (including my home, Canada,) melatonin is available in any pharmacy as an over-the-counter drug, while cortisol requires a prescription. Cortisol is restricted as a prescription drug likely as it shuts down the adrenal glands upon being consumed in any noticeable amount.
Please contact me if you have any key points about either cortisol or melatonin that you think should be added to the list of points above, and if you haven't already watched it, I hope you can take some time to watch this show!

*Note: The diagram used at the top was taken from this blog posting that has ten pieces of advice regarding healthy sleep patterns.

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