Individual differences in psychophysiological measures appear to influence personality characteristics in adolescent females exposed to child maltreatment, according to new research published in the journal Development and Psychopathology.

“We know that child maltreatment is a major public health issue that influences the physical and mental health of victims long-term. In addition to adverse life experiences, personality level factors such as extraversion and neuroticism can serve as risk and resiliency factors for the development of mental health difficulties,” said study author Raha Hassan of McMaster University.

“Considerably less is known about what factors influence personality in individuals who have experienced child maltreatment. I became interested in examining whether physiological factors previously implicated in reactivity and regulation could inform us about the development of personality in maltreated populations for these reasons.”

The researchers examined 55 adolescent girls who had experienced childhood maltreatment and a control group of 25 adolescent girls who were matched with maltreated participants on age, sex, handedness, and postal code. The participants underwent electroencephalogram and electrocardiogram tests to assess their brain activity and heart rate variability, and then completed a self-reported personality measure

Participants in the maltreated group were assessed again 6 and 12 months after their first visit.

The researchers found that maltreated participants with lower left frontal brain activity tended to become more extraverted over time, while those with lower variation in heart rate during the breathing cycle tended to become more neuroticism over time.

The findings indicate that “personality at any given time can be influenced by the physiological factors that support the ways we react and interact with our environment,” Hassan told PsyPost.

The study also provides support for Hans J├╝rgen Eysenck’s theory of personality. “Nearly 70 years ago, Eysenck proposed a two-factor model of personality in which he argued that individual differences in extraversion and neuroticism had a biological basis,” the researchers wrote in their study.

Eysenck’s theory “proposed that extraversion was maintained by chronic underarousal, and this underarousal motivated and facilitated approach-related behaviors, while neuroticism was largely maintained by overarousal, and this overarousal motivated and facilitated avoidance-related behaviors.”

“I hope readers learn that early personality theorists like Eysenck provide us with valuable models for human development that may extend to individuals exposed to early life adversity, in addition to typically developing populations,” Hassan said.

The study — like all research — includes some limitations.

“The most important caveat to keep in mind is that we were unable to collect data at three time points in the control participants like we did with the participants who experienced child maltreatment,” Hassan said.

“For these reasons, we cannot determine whether there were differences between maltreated and control participants in the influence of physiology on the trajectories of personality characteristics, preventing us from determining whether reported results were largely due to individual differences in personality or due to the effects of maltreatment. It would be helpful to replicate this study in the future with a control group followed over time in order to clarify these caveats.”

The study, “Psychophysiological influences on personality trajectories in adolescent females exposed to child maltreatment“, was authored by Raha Hassan, Harriet L. MacMillan, Masako Tanaka and Louis A. Schmidt.