The runner’s euphoria and opioids

The runner’s high is most likely due to release of the endorphins binding to the opioid receptors according to Boecker et al. (2008, doi: 10.1093/cercor/bhn013). Image courtesy of Pixabay.

We all know that exercise is good for you: it keeps you fit, it reduces stress and improves your mood. And also, sometimes, particularly after endurance running, it gets you high. The mechanism of euphoria reported by some runners after resistance training is unknown. Here is a nice paper trying to figure it out.

Boecker et al. (2008) scanned 10 trained male athletes at rest and after 2 hour worth of endurance running. By “trained athletes” they mean people that ran for 4-10 hours weekly for the past 2 years. The scanning was done using a positron emission tomograph (PET). The PET looks for a particular chemical that has been injected into the bloodstream of the subjects, in this case non-selective opioidergic ligand (it binds to all opioid receptors in the brain; morphine, for example, binds only to a subclass of the opioid receptors).

The rationale is as follows: if we see an increase in ligand binding, then the receptors were free, unoccupied, showing a reduction in the endogenous neurotransmitter, that is the substance that the brain produces for those receptors; if we see a decrease in the ligand binding it was because the receptors were occupied, meaning that there was an increase in the production of the endogenous neurotransmitter. The endogenous neurotransmitters for the opioid receptors are the endorphins (don’t confuse them with epinephrine a.k.a. adrenaline; different systems entirely).

After running, the subjects reported that they are euphoric and happy, but no change in other feelings (confusion, anger, sadness, fear etc.; there was a reduction in fear, but it was not significant). The scanning showed that it was less binding of the opioidergic ligand in many places in the brain (for the specialist, here you go: prefrontal/orbitofrontal cortices, dorsolateral prefrontal cortex, anterior and posterior cingulate cortex, insula and parahippocampal gyrus, sensorimotor/parietal regions, cerebellum and basal ganglia).

Regression analysis showed that there was a link between the euphoria feeling and the receptor occupancy: the more euphoric the people said they were, the more endorphines (i.e. endogenous opioids) they had bound in the brain. This study is the first to show this kind of link.

Reference: Boecker H, Sprenger T, Spilker ME, Henriksen G, Koppenhoefer M, Wagner KJ, Valet M, Berthele A, & Tolle TR. (Nov 2008, Epub 21 Feb 2008). The Runner’s High: Opioidergic Mechanisms in the Human Brain. Cerebral Cortex, 18:2523–2531. doi:10.1093/cercor/bhn013. Article | FREE FULLTEXT PDF

By Neuronicus, 28 November 2015

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64% of psychology studies from 2008 could not be replicated

Free clipart from http://www.cliparthut.com

It’s not everyday that you are told – nay, proven! – that you cannot trust more than half of the published peer-reviewed work in your field. For nitpickers, I am using the word “proven” in its scientific sense, and not the philosophical “well, nothing can be technically really proven, etc…”

In an astonishing feat of collaboration, 270 psychologists from all over the world replicated 100 of the most prominent studies in their field, as published in 2008 in 3 leading journals: Psychological Science (leading journal in all psychology), Journal of Personality and Social Psychology (leading journal in social psychology), and Journal of Experimental Psychology: Learning, Memory, and Cognition (leading journal in cognitive psychology). All this without any formal funding! That’s right, no pay, no money, no grant (there was some philanthropy involved, after all, things cost). Moreover, they invited the original authors to take part in the replication process. Replication is possibly the most important step in any scientific endeavor; without it, you may have an interesting observation, but not a scientific fact. (Yes, I know, the investigation of some weird things that happen only once is still science. But a psychology study does not a Comet Shoemaker–Levy 9 make)

Results: 64% of the studies failed the replication test. Namely, 74% social psychology studies and 50% cognitive psychology studies failed to show significant results as originally published.

What does it mean? That the researchers intentionally faked their results? Not at all. Most likely the effects were very subtle and they were inflated by reporting biases fueled by the academic pressure and the journals’ policy to publish only positive results. Is this a plague that affects only psychology? Again, not at all; be on the lookout for a similar endeavor in cancer research and rumor has it that the preliminary results are equally scary.

There would be more to say, but I will leave you in the eloquent words of the authors themselves (p. aac4716-7):

“Humans desire certainty, and science infrequently provides it. […]. Accumulating evidence is the scientific community’s method of self-correction and is the best available option for achieving that ultimate goal: truth.”

Reference: Open Science Collaboration (28 August 2015). PSYCHOLOGY. Estimating the reproducibility of psychological science. Science, 349(6251):aac4716. doi: 10.1126/science.aac4716. Article | PDF | Science Cover | The Guardian cover | IFLS cover | Decision Science cover

By Neuronicus, 13 October 2015