Exam Stress and Genetics

5 minute read
Originally posted here: https://mcgill.ca/oss/article/health-general-science/exam-stress-and-genetics

I don’t know about you, but I just cannot stand exams. Give me research projects, essays, even practical lab examinations, and I excel.

But something about sitting at a desk, staring at a scantron and being expected to pour knowledge out of my head just makes me freeze up and score, well, let’s just say I sometimes ride the bell curve. Luckily, it seems like I’m not alone.

A 2009 study that looked at 779 Taiwanese students has found an interesting link between Catechol-O-methyltransferase (COMT), an enzyme that catalyzes the body’s degradation of dopamine, and test performances under high stakes circumstances. The COMT enzyme is encoded by the COMT gene, and is responsible for removing dopamine, epinephrine and norepinephrine from the brain. Specifically, the prefrontal cortex which is responsible for many things, such as fear and emotional processing.

The COMT gene has an interesting feature- a single nucleotide polymorphism (SNP). All of our DNA is made of strings of nucleotides, which are read and used like instructions for making proteins out of amino acids. In an SNP, just 1 nucleotide is changed, which changes the amino acid the recipe calls for, and the protein that is built. Specifically, for the COMT gene, it causes the change from the amino acid valine to the amino acid methionine at position 158 of the protein (written as Val158Met). Due to the polymorphism, the COMT gene can have 2 forms, which means the COMT protein can have 2 forms as well. This protein happens to be an enzyme, and though both forms are functional, they do function slightly differently. With the Val variant of the gene, dopamine is broken down at a rate up to 4 times faster than with the Met variant. This means than for people expressing the slower Met variant, their brains are flooded with excess dopamine, as it is not being broken down rapidly enough.

Tests have shown that individuals with the slow Met variant have a cognitive advantage over those with the fast Val variant. The excess of dopamine seems to increase neuronal signaling and allow people to reason, focus and problem solve better. With the fast Val variant, people’s prefrontal cortexes don’t seem to have enough dopamine to function at the level of their slow Met peers.

When you throw school exams and high stress into the mix however, things get tricky. Under high pressure, the brain produces quite a bit of excess dopamine, and you’d think that’d be an advantage, but in reality it’s just too much of a good thing. The regulation of dopamine is actually a pretty tight system, so under the high-stress, high-dopamine conditions, the slower acting Met variant just can’t keep up. The excess of neurotransmitter messes with the way the brain makes and values decisions. Dopamine is highly involved in decision making processes and reward pathways, so you can imagine that brains operating outside of the normal dopamine equilibrium aren’t functioning at their best.

The 2009 study in Taiwan looked at 779 students about to take their Basic Competency Test, an intense that determines what high schools students may attend. The test lasts for 2 days, and only 39% of students pass, so it is an ideal situation to look at academic performances under stressful situations. As expected, the Taiwanese students with the slow-acting Met variation scored on average 8 percent lower than those with the fast-acting Val variation.

So those with the faster Val variant of the COMT gene perform best under pressure, and those with the slower Met variant perform best under normal, non-stressful conditions. I think we all can guess, no genetic test needed, which variation I have. Though in truth, it is slightly more complicated than this. Because we all get 1 copy of a gene from the sperm donor, and 1 from the egg donor, it’s possible to be homozygous Val (Val/Val), homozygous Met (Met/Met) or heterozygous (Val/Met). Hypothetically 25% of the population would carry each homozygous variation, and 50% would be heterozygous, which potentially explains why in every class there seems to be several people freaking out on exam day (like me), and several people who don’t appear to care, but most students seem to fall somewhere between the two extremes.

The COMT gene and enzyme have also been studied in regards to their effects on a number of other conditions. A 2005 study found that individuals expressing the Val/Val or Val/Met variations were more likely to exhibit psychosis symptoms or develop schizophrenia in adulthood following adolescent marijuana use (though this study disagrees). A 2007 study examined the various forms of the COMT gene and its relation to how individuals experience ‘positive affect’. It found that the more Met alleles that one had increased one’s ability to experience rewards, with Met/Met individuals reporting the same amount of positive affect from a ‘bit pleasant event’ as Val/Val individuals did from a ‘very pleasant event’.

The Val158Met polymorphism has also been examined for its potential role in major depressive disorderdomestic abuse during pregnancy and childhood ADHD.

These genetic differences can inspire some interesting debates about whether standardized testing should be standard in schools, and whether high-stress situations allow all students to shine. Taiwan, for instance, has stopped the Basic Competency Test as of 2014, but exams like the MCAT or LSAT remain the norm elsewhere.

For now at least, exams will certainly continue, and I will continue to choose classes with lab or essay options over those with sit-down finals every time.