The Adventurer's Gene

Ryan Argetsinger, 8/13/24

       It’s fair to say that the average person experiences highs and lows of varying degrees. Some may span for weeks, months, even years, but the tipping of the scale, ride on the roller coaster, always flips to the other side of a coin. However, some may emphatically experience these mood changes more emphatically than others. 

Bipolar disorder is a mental health condition that is characterized by intense mood swings, ranging from manic episodes of euphoria, extreme joy, and enthusiasm, to even mania, to deep depressive episodes. The frequency and range of intensity in these episodes can vary among patients, leading to behavioral changes, risk-taking, anger, sadness, and even suicidal ideology. In terms of treatment for bipolar disorder, the most well-researched and effective is cognitive behavioral therapy with a mixture of antipsychotic-antidepressants. Most patients may even suffer from additional mental health needs, such as anxiety and trauma, which may require anti-anxiety and mood-stabilizing medications. With treatment for mental health still, in an era of developmental progress, it’s necessary to consider the potential causes for bipolar disorder. The current understanding is that there are physiological differences in neurobiology and neurochemistry seen in brain scans of patients with bipolar disorder, in comparison to non-bipolar brains. This helps to target areas of the brain that may be indicative of neural pathways related to behavioral changes; however, due to the still unknown complexity of the brain, multiple regions could light up at any moment on a PET scan to show just how many regions of the brain can light up in variability. The other well-known factor is that bipolar disorder can be fairly hereditary. It’s more common for family members with bipolar disorder to inherit it from a relative who may have it, but a greater question is where would such a mentally devastating genetic composition arrive from. 

Evolutionary psychologists may have a better understanding of how the interactions between dopamine, bipolar disorder, and genetics have brought us to our current history of the world today, by evaluating cohort studies across the world. In populations like Japan and India, bipolar disorder was found prevalent in only 0.7 and 0.1% of the population, while the U.S. exhibited a prevalence rate of 4.4%. 

Now, what’s something in common with our ancestors who crossed from Asia to North and South America, that most Americans and their families have previously done? If you stated: that they traveled from one continent to another with the unknown uncertainty (risk) for a better life, you’d be correct. If there’s one thing that has forced genetic change, it’s adaptation. The adaptation and need to survive, to chase a pack across an unknown terrain, to search for better land, or to find a new home, is something that allows humanity to cross oceans, climb mountains, and risk their lives for the hope of a better one. Genetics comes into play when dopamine, a neurotransmitter responsible for functional planning and long-term goals, is also related to risk-seeking behavior. The idea of a reward, so big, that it's worth the risk, is not something that everyone is worth pursuing, but some individuals are more predisposed to such behaviors. There is evolutionary and anthropologic evidence to show that some populations have higher frequencies of expression for DAT1, which is a dopamine transporter gene. Researchers have shown that this gene's expression may be linked more to those behaviors of novelty seeking and harm avoidance, which are common traits in bipolar disorder. With that being said, novelty seeking is necessary in circumstances of going to a foreign land without a safety net of return. 

The currency hypothesis of bipolar disorder being associated with dopamine expression is one that is being further investigated and explored. Some believe that it’s the infrequency and range of dopamine release that leads to these manic states, while the lack of dopamine can lead to depressive episodes. While neuroscience is still a newer field in biomedical sciences, it’s worthwhile to understand how epigenetics, epidemiology, and our human history may be the start of a greater understanding of neuropsychiatric physiology and treatment. 

References

Mayo Clinic, "Bipolar Disorder"

https://www.mayoclinic.org/diseases-conditions/bipolar-disorder/symptoms-causes/syc-20355955 

CNN, "U.S. has highest bipolar rate in 11-nation study"

http://www.cnn.com/2011/HEALTH/03/07/US.highest.bipolar.rates/index.html#:~:text=The%20U.S.%20ranked%20higher%20in,relatively%20high%20prevalence%20of%202.6%25. 

Springer, "Dopamine transporter gene may be associated with bipolar disorder and its personality traits"

https://link.springer.com/article/10.1007/s00406-014-0570-0