What came first, the chicken or the egg? Are we born with our own unique personality or is the environment in which we are born and raised responsible for shaping it?
In an article recently published in the Journal of New Ideas in Psychology, authors John E. Krzeczkowski from the Neuroscience Graduate Program and Ryan J. Van Lieshout from the Department of Psychiatry and Behavioural Neurosciences at McMaster University in Canada attempt to answer these questions by examining the current science behind "Prenatal Influences on the Development and Stability of Personality."
What they found is that although there is abundant evidence to show how prenatal stress can cause adverse mental health outcomes in children that continue on into adulthood, there is little research on the stability of personality traits into adulthood which altered by prenatal stress. In other words, sure, it can be shown that prenatal stress can affect our personality in the short term, making us more laid back or open to new ideas or the opposite, rigid and closed-minded, or even neurotic, but there isn't enough research that follows children into adulthood to see whether these personality traits can change over time or if we are who we are basically, from the day we come into this world.
Let's define personality.
According to one of the leading theories on personality, the “Five-Factor Model", there are five dimensions of personality: openness, conscientiousness, agreeableness, extraversion, and neuroticism that influence our behaviour across the lifespan. While some studies show how our adult personality traits can be observed as early as childhood, others point out that our personalities have the ability to change depending on what’s happening in our life and especially during important developmental stages like parenthood. Neither negates the fact, however, that personality traits can also be shaped while in the womb, say researchers.
And here’s how.
Going as far back as the Paleolithic era, researchers believe fetuses have evolved to be able to prepare themselves neurologically for the condition of their postnatal environment. This is called “prenatal programming”. If a fetus senses through stress from its mother that its postnatal world will be a harsh and stressful environment, in order to increase their changes of survival, the fetus will alter its neurodevelopmental brain to become more vigilant and sensitive to stimuli in order to be ready to defend itself. In the Paleolithic era, this would correlate to defending itself from predators and scarce resources but since our fear response hasn’t evolved much since Paleolithic times, stress is stress for the fetus no matter whether it’s stress from escaping the attack of a sabretooth tiger or stress felt from malnutrition, or stress from its mother's maternal mental health disorder, such as prenatal depression. If the stress level is high enough, a fetus will alter its own stress response, which in turn, could also alter its personality.
What happens biologically, is that during pregnancy, whenever a mom is stressed, the stress hormone, cortisol, is released into the placenta. If the mom isn’t too stressed, 80% of the cortisol is metabolized by an enzyme before it reaches the fetus. If the mom is over stressed or highly stressed, to put it simply, the enzyme doesn’t work properly, and the fetus becomes exposed to high levels of cortisol which the developing brain adjusts to by altering its hypothalamus and amygdala, the two regions that control our fear response. This heightened fear response contributes to increased anxiety and hyperactivity postnatally and researchers believe it can also alter our personality.
Researchers have found that overweight babies as well as underweight babies are more prone to “maladaptive” personality traits, emotion dysregulation and psychiatric disorders as an adult. Babies born to obese mothers are at a higher risk of developing autism and babies born to mothers with high levels of stress are at a higher risk of developing attention deficit hyperactivity disorder. Personality traits such as neuroticism were observed in people aged 20 who were born preterm and neurotic adults over the age of 60 have been shown to have had lower birth weights.
The authors of the current article believe it’s important to research the effect prenatal stress has on personality as well because “certain personality traits can increase the risk for psychopathology (e.g., high neuroticism leading to depression and/or anxiety disorders).” They content that we need to better understand the links between prenatal stress and how it influences our personalities as children and as adults so we can “shed light on relations between psychopathology and personality” and how they might influence one another.
Research Gate, (January 2018), John E. Krzeczkowski, Ryan J. Van Lieshout, Prenatal influences on the development and stability of personality, https://www.researchgate.net/publication/323149545_Prenatal_influences_on_the_development_and_stability_of_personality