The link between neuroticism and brain structure may not be as straightforward as once thought. New research suggests that neuroticism is associated with lower total brain volume, but this relationship only holds true for individuals with low behavioral adjustment. In contrast, those who are more adaptable to changing life situations seem to be shielded from the potential negative effects of neuroticism on brain volume. These findings, published in the Journal of Personality, provide new insights into how personality traits interact with coping mechanisms to influence brain health.
Neuroticism is a personality trait characterized by a tendency to experience frequent and intense negative emotions, such as anxiety, worry, anger, and sadness. Individuals high in neuroticism are more likely to perceive situations as threatening or challenging and often have a heightened sensitivity to stress. This trait is associated with greater vulnerability to mental health disorders, including anxiety and depression, as well as difficulties in coping with everyday stressors.
Neuroticism is considered one of the five major dimensions of personality in the Five-Factor model of personality, which also includes openness, conscientiousness, extraversion, and agreeableness.
Previous studies have shown that individuals high in neuroticism exhibit patterns of brain activity indicative of chronic stress and difficulty regulating emotions. For example, they tend to have a more reactive amygdala, a brain region involved in processing emotions like fear and anger. Additionally, there is decreased connectivity between the amygdala and the prefrontal cortex, which is responsible for higher cognitive functions such as decision-making and impulse control. These individuals also often have reduced gray matter volume, which comprises the brain’s neuronal cell bodies and dendrites.
Study author Qinggang Yu and his colleagues noted that higher levels of neuroticism are associated with lower total brain volume after controlling for the volume of space inside the skull (intracranial volume). However, there is evidence that this association might be attenuated or even reversed in individuals with high behavioral adjustment.
Behavioral adjustment refers to one’s ability to modify actions and responses to better align with the demands and expectations of a specific environment or situation. The study authors aimed to test whether behavioral adjustment modifies the link between neuroticism and brain volume.
They analyzed data from the Midlife in the United States study, a long-term research project investigating factors influencing physical and mental health, well-being, and aging processes among adults in the United States, with a focus on the midlife period. More specifically, they used data from the “refresher” group, a probabilistic sample of 3,577 U.S. residents, plus 508 Black Americans from Milwaukee, WI. Of these individuals, 127 underwent magnetic resonance imaging, and their data were used in the analysis. Sixty-seven of them were female, and their average age was 49 years.
Participants completed an assessment of neuroticism using a 31-item adjective list, and an assessment of behavioral adjustment using a 5-item scale (e.g., “When values held by others sound more reasonable, I can adjust my values to theirs,” “I usually follow the opinions of people I can respect,” or “Once something has happened, I try to adjust myself to it because it is difficult to change it myself”). In their analyses, the study authors also controlled for differences in intracranial volume, age, sex, race, education, and conscientiousness.
Results showed that the association between neuroticism and total brain volume is too small for researchers to be confident that it is not just random. This remained the case after controlling for intracranial volume, age, sex, race, education, and conscientiousness.
Further analyses revealed that this association depends on behavioral adjustment. In participants with high behavioral adjustment, there was no link between neuroticism and total brain volume. However, in participants with low levels of behavioral adjustment, those with higher levels of neuroticism tended to have lower brain volumes.
“Our data are consistent with the hypothesis that neuroticism sensitizes people to perceive threat cues and experience stress. For those lacking the ability or willingness to adjust one’s behavior to cope with situational demands, neuroticism may magnify the stress, thereby deregulating the hypothalamic–pituitary–adrenal axis. The resulting rise of cortisol could be associated with atrophy of brain tissue. For those who are both able and willing to adjust their behaviors to cope with various situations, physiological pathways for regulating stress could remain intact, which attenuates the link between neuroticism and potential neurodegeneration,” the study authors concluded.
The study sheds light on the links between brain volume and neuroticism. However, while the study authors interpret the results as a likely effect of neuroticism on brain volume, the design of the study itself does not allow any cause-and-effect conclusions to be drawn from the data. While it is possible that neuroticism leads to brain atrophy in the way proposed by the authors, it would be necessary to demonstrate that it is not some aspect of brain structure, observed as reduced brain volume, that produces high levels of neuroticism.
The paper, “Behavioral adjustment moderates the effect of neuroticism on brain volume relative to intracranial volume,” was authored by Qinggang Yu, Stacey M. Schaefer, Richard J. Davidson, and Shinobu Kitayama.
