The New Science On The Hippocampus, Self-Esteem, And Physical Health
Happiness is nothing more than good health and a bad memory. —Albert Schweitzer
The hippocampus is a key area of the brain involved with basic function, part of the temporal lobe and intimately related with the amygdala. The hippocampus is involved with memory storage and retrieval, while the amygdala is best known for its role in fear and alarm in the face of potential threats. When functioning properly, the hippocampus is thought to create an appropriate context for memories, helping to support a coherent narrative of what is and is not really dangerous, keeping the amygdala regulated so that it is active only when appropriate…and buffering against excess stress, both from the environment and internally-generated.
Posttraumatic and Stress-Related Effects
In conditions where fear-based responses have become poorly regulated, such as PTSD, the hippocampus has been found to be smaller in size and less effective at grounding the alarm signaling of the amygdala. It isn’t clear whether having a smaller hippocampus is the result of trauma, a factor which predisposes to developing PTSD, or both. While there are many studies showing an association between PTSD and other psychiatric conditions, and smaller hippocampi, there are only small twin studies comparing traumatized with non-traumatized twins suggesting that smaller hippocampi may be a risk factor for subsequent PTSD. On the other hand, animal studies have shown that chronic stress directly reduces the size of the hippocampus, and effective treatment can increase the size of the hippocampus and other brain regions. Most likely, there are complex two-way relationships among hippocampus size, environmental factors, and risk for positive and negative impacts on well-being.
Such persistent activation of threat-response systems when no threat is present is associated with negative health effects due to connections between the hippocampus and other parts of the brain, including the HPA-axis (hypothalamic-pituitary-adrenal) which regulates stress hormones such as cortisol and adrenaline in the brain and body. In fact, the hippocampus has been found to play a role in well-being beyond its role in PTSD.
Self-Esteem, Health, and the Hippocampus
In recent research (Lu, Li, Wang, Song and Liu, 2018), study authors highlight the role of the hippocampus for both self-esteem and physical health, seeking to understand if the hippocampus is part of the brain circuitry connecting self-esteem and greater physical health. In reviewing the prior literature, researchers offer key observations. First, higher self-esteem is associated with better health outcomes and longevity, likely via higher reported levels of positive states including optimism, relaxation, gratitude, and joy. Lower self-esteem, in contrast, is associated with negative health outcomes, with increased risks for depression and anxiety, smoking and alcohol use, and increased risk for cardiovascular and other diseases.
Second, the hippocampus is closely involved with self-esteem. This makes sense given that the hippocampus is involved with autobiographical memory, a key part of our sense of self and identity, how we feel about ourselves and the stories we tell ourselves and others about who we are. Neuroimaging research has shown that the hippocampus is larger and more active in people with greater self-esteem. Finally, the hippocampus is connected not just with psychiatric problems, but also plays a role in physical health. Research has shown, for example, that the hippocampus is smaller in size in Type 2 diabetes, hypertension, chronic jet lag, and inflammation. The hippocampus is larger, on the other hand, in people with greater aerobic fitness, suggesting it may play a role in overall health.
Does the Hippocampus Connect Self-Esteem with Physical Health?
Given these observations, Lu and colleagues hypothesized that the hippocampus might be part of the underlying brain circuitry connecting self-esteem and physical health. In order to answer this question, they recruited 239 college students for a neuroimaging research study looking at the following factors: self-esteem, via the Rosenberg Self-Esteem Scale (RSES); physical health, via the Chinese Constitute Questionnaire (CCQ), a standard, validated measurement tool of general physical health; and structural MRI (magnetic resonance imaging), to look at the size of the hippocampus in study participants. Researchers then analyzed the data and performed a “mediation analysis” to determine what, if any, role hippocampal volume had in mediating the relationship between self-esteem and physical health.
First, they found that self-esteem and physical health were significantly correlated with one another in their study, confirming the results of prior research. They also showed that in this group of participants self-esteem and hippocampal volume were positively correlated for both left and right sides of the brain. The larger the hippocampi, the greater the reported self-esteem. Furthermore, they also found a positive correlation with hippocampus size and physical health, again for both the left and right sides. Replicating the findings of previous research, they reported three key relationships: 1) self-esteem and physical health; 2) larger hippocampus and self-esteem; 3) larger hippocampus and physical health.
However, while suggestive, these findings alone don’t provide evidence that the hippocampus is a primary player in determining how higher self-esteem leads to better physical health. In order to see whether the hippocampus is part of the neural pathway connecting self-esteem and physical health, researchers analyzed the data to see whether the connection between self-esteem and physical health remained as robust after factoring out the role of the hippocampus. In other, words, we can see how much the hippocampus mediates between self-esteem and physical health by subtracting the contribution of the hippocampus and seeing what is left over. When study authors performed this mediation analysis, they found that there was a statistically significant decrease in the correlation between self-esteem and physical health, showing that hippocampal size is a key factor connecting the two. However, self-esteem and physical health were still related, independent of the hippocampus, showing that it is not the only factor connecting the two.
What can We do to Enjoy Greater Self-Esteem and Physical Well-Being?
This is an early yet intriguing finding suggesting that the hippocampus has a primary, but not exclusive, role in determining how self-esteem leads to better physical health. It is tempting to speculate about the role of the hippocampus in identity and sense of self as an overarching influence in providing a good sense of self, secure attachment and healthy relationships with others, and as a result better self-care, especially given how trauma can interfere with physical and emotional health, and impair self-care.
On a basic level, however, the hippocampus is involved with regulating key physiological factors, balancing stress and relaxation responses depending on the context, under the influence of “top-down” factors from higher brain centers involved with executive function and conscious control of behavior. Future research can look in more detail at other brain networks involved in hippocampal control, in order to find ways to optimize physical health as mediated by self-esteem, to understand what specific behaviors may influence hippocampal function to foster greater health and whether existing and new treatments can target key brain regions to be more effective. Does increasing self-esteem increase the size and function of the hippocampus? If so, what are the specific mechanisms? How does aerobic exercise increase hippocampus size, and how much of the health benefits are the result of an altered hippocampal function? What tools can we develop to leverage understanding the role of the hippocampus on health? Is the hippocampus involved in the positive effects of gratitude, self-compassion, and happiness on well-being, shifting the stories we tell ourselves about who we are in literally healthier ways?
How much of a role does the hippocampus play in ensuring we can have healthy relationships with others, a factor which is also associated with better physical health? It makes sense to keep doing things we know help us feel better about ourselves, enjoy greater self-esteem and self-efficacy, and do more of what makes us feel better and be healthier while looking forward to understanding how best to use emerging brain science to provide additional tools for improving health and quality of life.
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