The following is a paper I wrote for my developmental psych class, in response to a study we read in the course:
The goal of the Tottenham et al. study was to track the volumes of the amygdala and hippocampus in relation to length of exposure to institutional child-rearing and the presence of internalizing behaviors and anxiety. Researchers measured the brain structures using magnetic resonating imaging (MRI) and the behaviors with a structured interview and two behavioral questionnaires. The researchers hypothesized that larger amygdala volume in previously institutionalized children is associated with longer time spent in the institution (thus longer exposure to early-life stress), and in turn that larger amygdala volume is positively correlated to anxiety and internalizing behaviors (Tottenham et al., 2009).
Previous human studies show that previously institutionalized children have higher rates of anxiety disorders, and that adults that have anxiety also have larger amygdalae, while adults who have undergone major stress or trauma also have lower hippocampal volume. However, studies of children in relation to hippocampal size and stress do not show this result, which may suggest hippocampal recovery after early-life stress (Tottemham et al., 2009). These previous studies were used in to predict that amygdala volume would have a higher correlation with anxiety and internalizing behaviors than the hippocampus.
This study also measures length of exposure time in child-rearing institutions based on the research by Nelson et al. on rhesus monkeys, which showed that timing of the separation of infant and mother monkey influences emotional behavioral problems (Tottenham et al., 2009). Timing could have a similar effect contributing to the behavioral difficulties of previously institutionalized children.
The subjects totaled seventy-eight children, thirty-eight of whom had been previously institutionalized. A slight majority of those previously institutionalized children showed signs of psychiatric disorders from the outset of the study, including eighteen percent who qualified as having an anxiety disorder. The previously institutionalized group and non-institutionalized group were comparable in socioeconomic status. The study measured for age at adoption, with older adopted children having more time spent raised in institutions and less time with the family, whereas younger adopted children had less time in institutions and thus more time with the family. Early adopted children were defined as younger than fifteen months old, and late adopted children were defined as older than fifteen months old (Tottenham et al., 2009).
Based on these ages, the groups were further divided into four final groups: early-adopted, late-adopted, and two control groups consisting of non-institutionalized children. Both neuroimaging and behavioral assessments were conducted on these four groups, which consisted of structural MRI, structured interviews, and internalizing and anxiety questionnaires such as the Child Behavior Checklist (CBCL) and Screen for Child Anxiety Related Emotional Disorders (SCARED), which were completed by the parents and controlled for with the Wechsler Abbreviated Scale of Intelligence IQ test. . The MRI provided volumetric data on the specific brain structures of interest, the amygdala, the hippocampus, and the caudate, which was measured for control. The questionnaires provided additional data relating to internalizing and anxiety disorders that were used for comparison to the sizes of these brain structures (Tottenham et al., 2009).
The study’s findings from the MRI data showed that late-adopted children had significantly larger amygdala volumes than the early-adopted group and both control groups. Researchers also found that a positive correlation exists between amygdala volume and age at adoption. Hippocampal volume was not significantly different, unlike the previous animal studies that showed smaller hippocampal volume after stress (Tottenham et al., 2009). The study’s findings from the behavioral data showed that larger amygdala volume also positively correlated with scores from the CBCL and SCARED tests, which indicates that larger amygdalae were present in children whose parents rated higher levels of internalizing and anxiety-related behaviors (Tottenham et al., 2009). These data also support the hypothesis.
These data suggest that early-life stress (in this case resulting from institutionalized child care) can result in a highly developed amygdala, which in turn correlates to an increased prevalence of internalizing behaviors and anxiety. Disturbances in attachment, the process of bonding to a primary caregiver, may explain these findings. Institutional child-rearing settings do not often allow for the deep one-on-one connection between caregiver and child that results in attachment. For example, some institutions have a ratio of twenty children to one caregiver, which can lead to unstable relationships (Tottenham et al., 2009). According to studies, children who are attached to a caregiver are more confident and mature, while non-attached children show greater risk for emotional and interpersonal difficulties (Belsky, 2010). This information is consistent with the study’s findings, in that both attachment disturbances and larger amygdala volume correlate with these internalizing behaviors (fear, social inhibition, and depression) and anxiety (Belsky, 2010). Attachment disturbances related to the stressful reality of institutional care may play a role in the larger amygdala volume results in this study.
The amygdala serves the function of recognizing emotional cues and aids emotional expression. It is a part of the limbic system, which as a whole processes emotional reactions, such as anxiety (Hansell & Damour, 2008). An imbalance in development of these brain structures in relation to the frontal lobe may produce confused social responses, according to a study by Yurgelin-Todd and Killgore (2006), which focused on the differences between adolescent and adult brains. Adolescents more often misinterpreted fearful facial expressions, which may be explained by their tendency to engage the amygdala versus the frontal cortex, like adults did. A larger amygdala volume may contribute to internalizing behaviors and anxiety because of these confused social responses. In addition, larger amygdalae are present and more often engaged in anxiety-prone children (Tottenham et al., 2009). This evidence in combination with the results of the study and prior attachment research supports the study’s hypothesis that a relationship exists between early life stress, amygdala volume, internalizing behaviors and anxiety.
A major limitation of this study is the lack of randomization in the sample. Adopted children in this case were not randomly assigned to their new families, which could affect the levels of internalizing behaviors and anxiety noted in the children. A child may have experienced a disproportional amount of stress in comparison to the other children based on other factors, such as culture shock. Alternatively, another child may have an exceptionally smooth transition into his or her new home due to more compatible cultural backgrounds. Both of these factors are possible without being influenced by amount of time spent in the institution.
Another limitation present in the study comes from its correlational design. While a relationship is evident between increased amygdala volume, behavioral issues, and longer time spent in the institution, this pattern may have another explanation. Behavioral problems may already exist in potentially adopted children, and may have a role in discouraging adoptive parents from selecting that child instead of another child who appears more psychologically fit. Instead of the length of time in the institution predicting these behavioral problems and larger amygdala volume, these behavioral issues may be the reason for the longer stay in the institution and the resulting amygdala growth.
Follow-up research for this study could involve a longitudinal study testing whether an intervention technique for newly adopted children could benefit these children in relationship to the development of amygdala volume and behavioral problems. Study participants would include a group of previously institutionalized children who were adopted after fifteen months of age and a control group of children who were never institutionalized. The study would measure for any amygdala recovery and behavioral problems over time, with the previously institutionalized children divided into two randomized groups: those who receive the intervention and those who do not. The control groups would be similarly divided. The intervention would entail a specific training program for parents designed to minimize potential culture shock and strengthen parent-child bonding early in the process. The use of MRI, CBCL and SCARED tests could be used in the same fashion as the current study. This follow-up study would be important to see if interventions of this type could be used to lessen the prevalence of internalizing behaviors and anxiety and/or reducing amygdala volume in adopted children. It is possible that the symptoms of an enlarged amygdala (internalizing behaviors and anxiety, according to the current study) could be lessened even without a change in amygdala volume. Finding a break in this amygdala-behavioral problem correlation by use of post-adoption interventions would be an intriguing finding.
The Tottenham et al. study is important because not only does it find larger amygdala volume in the late-adoption group, but it finds an overall correlation between age at adoption and amygdala volume. On top of that, the study finds that higher amygdala volume is related to higher parental ratings on the behavioral questionnaires. These three components make this study especially novel.
References
Belsky, J. (2010). Experiencing the lifespan (2nd ed.). New York. Worth Publishers.
Hansell, J., & Damour, L. (2008). Abnormal psychology (2nd ed.). United States of America.
Wiley & Sons, Inc.
Tottenham, N., & et al. (2009). Prolonged institutional rearing is associated with atypically
large amygdala volume and difficulties in emotional regulation. Journal compilation.
Retrieved from: https://ctools.umich.edu/access/content/group/da5a970e-dbf5-4f4d-8d72
d8280f4c505f/Paper%20Assignment%20_2/Tottenham%20et%20al%202010.pdf
Yurgelin-Todd, D. A., & Killgore, W. D.S. (2006). Fear-related activity in the prefrontal cortex
increases with age during adolescene: A preliminary fMRI study. Neuroscience letters.
Retrieved from: https://ctools.umich.edu/access/content/group/da5a970e-dbf5-4f4d-8d72-d8280f4c505f/Articles%20for%20Presentations/Yurgelun-Todd%20Killgore%202006.pdf
