IB Psych Paper 2 Studies Abnormal

Karl et al. (2006)

A Meta-Analysis of Structural Brain Abnormalities in PTSD

Karl et al. Aim

To investigate whether individuals with Post-Traumatic Stress Disorder (PTSD) show consistent structural abnormalities—particularly in the hippocampus and amygdala—compared to both trauma-exposed individuals without PTSD and non-traumatized controls. The study further aimed to assess whether these structural changes vary by age (adults vs. children) and whether trauma exposure alone can account for brain differences.

Karl et al. Participants

This was a meta-analysis, so no direct participants were studied.

The authors aggregated and analyzed data from 43 peer-reviewed structural neuroimaging studies of PTSD.

Included studies involved both adult and pediatric participants, as well as both trauma-exposed and non-trauma-exposed control groups.

Across studies, volumetric data were collected for brain regions including the hippocampus, amygdala, corpus callosum, and frontal lobes.

Karl et al. Methodology

Meta-analytic approach using data from published MRI studies that measured brain volume differences between PTSD and control groups.

Volumes of left/right hippocampus, left/right amygdala, frontal lobes, and corpus callosum were extracted from each study.

Effect sizes were calculated to determine the magnitude of structural differences between:

PTSD vs. trauma-exposed controls

PTSD vs. non-traumatized controls

Trauma-exposed vs. non-traumatized controls

Separate analyses were conducted for adults and children to examine developmental differences in PTSD-related brain structure changes.

Karl et al. Results Areas

Hippocampus, Amygdala, Other Brain Structures

Karl et al. Hippocampus Results

Adults with PTSD had significantly smaller hippocampal volumes than both trauma-exposed and non-traumatized controls.

Left hippocampal volume reduction was particularly pronounced.

Trauma-exposed controls (without PTSD) also had smaller hippocampi compared to non-exposed individuals, suggesting that trauma itself contributes to hippocampal reduction.

In children with PTSD, no significant hippocampal volume reductions were observed.

Karl et al. Amygdala Results

A smaller left amygdala volume was found in adults with PTSD.

No consistent differences were observed in pediatric PTSD samples or in the right amygdala.

Karl et al. Other Brain Structures Results

Frontal lobe and corpus callosum volume reductions were found in pediatric PTSD samples, suggesting a different pattern of brain vulnerability in children.

Karl et al. Significance

Hippocampal and amygdala abnormalities are robust neural correlates of adult PTSD, supporting the idea that prolonged or repeated exposure to trauma disrupts limbic system development and function.

The finding that trauma-exposed individuals without PTSD also have smaller hippocampi implies a dose-response relationship between trauma and hippocampal volume, but not necessarily a PTSD-specific effect.

Lack of hippocampal changes in pediatric samples suggests that such structural abnormalities may emerge later in development or as a consequence of chronic PTSD.

The observed left-lateralized reduction in the amygdala supports prior findings on hemispheric asymmetries in emotional processing and stress reactivity.

These structural findings reinforce models of PTSD that emphasize impaired memory consolidation, contextual fear learning, and dysregulation of emotional processing, involving hippocampal-amygdala-prefrontal circuitry.

Overall, the results align with a developmental psychopathology framework in which the timing and severity of trauma interact with brain development to produce variable outcomes.

Gilbertson et al (2002)

Twin Study of Hippocampal Volume and PTSD Vulnerability

Gilbertson et al Aim

To determine whether smaller hippocampal volume is a predisposing risk factor for developing Post-Traumatic Stress Disorder (PTSD) after trauma exposure—or whether it is a consequence of trauma.

The study addressed this question using a monozygotic twin design, where only one twin had been exposed to combat in Vietnam. This allowed the researchers to distinguish inherited brain structure differences from trauma-related brain changes.

Gilbertson et al. Participants

Total N = 34 male monozygotic (identical) twin pairs (68 individuals)

In each pair:

One twin was a combat-exposed Vietnam veteran (Exposed Twin, or “ET”)

The other was a non-exposed co-twin (Non-Exposed Twin, or “NET”)

Two subgroups:

PTSD Group: 17 twin pairs in which the combat-exposed twin had PTSD

Non-PTSD Group: 17 twin pairs in which the combat-exposed twin did not have PTSD

Twins were all biologically identical, allowing for control of genetic factors

Gilbertson et al. Methodology

Design: Correlational twin study with MRI imaging

MRI scans were used to measure hippocampal volume bilaterally (left and right) in both the combat-exposed and non-exposed twins.

Clinical interviews and standardized assessments (e.g., Clinician-Administered PTSD Scale, CAPS) were used to diagnose PTSD and measure symptom severity.

Researchers compared hippocampal volumes across:

Twins with PTSD vs. without PTSD

Their respective non-exposed co-twins

Across all combinations to assess heritability vs. trauma effects

Gilbertson et al. Results

Combat-exposed twins with PTSD had significantly smaller hippocampal volumes compared to combat-exposed twins without PTSD.

Non-exposed co-twins of PTSD-affected veterans also had smaller hippocampal volumes, even though they had never experienced trauma or developed PTSD.

Hippocampal volume was highly correlated within twin pairs, regardless of trauma exposure.

Smaller hippocampal volume in non-exposed co-twins predicted the severity of PTSD symptoms in the exposed twin.

Gilbertson et al. Significance

This was one of the first studies to demonstrate that smaller hippocampal volume is a pre-existing risk factor for developing PTSD, not just a consequence of trauma.

The findings suggest that hippocampal volume may reflect a genetic or developmental vulnerability to stress-related disorders.

Supports a diathesis-stress model: individuals with a biological vulnerability (in this case, reduced hippocampal volume) are more likely to develop PTSD when exposed to trauma.

Reinforces the importance of the hippocampus in contextual memory and fear regulation, which are commonly impaired in PTSD.

Provides a methodological advance by using monozygotic twin controls, a powerful design for separating cause and effect in neuroimaging research.

Hitchcock et al.

The Role of Negative Appraisals and Social Support in Predicting PTSD Symptoms in Children

Hitchcock et al. Aim

To examine whether negative cognitive appraisals shortly after trauma exposure predict the severity of PTSD symptoms in children six months later.

A secondary aim was to explore whether social support influences PTSD symptoms indirectly by shaping children's cognitive appraisals of the trauma.

The study is grounded in Ehlers and Clark's (2000) cognitive model of PTSD, which suggests that negative appraisals and maladaptive processing contribute to PTSD development.

Hitchcock et al. Participants

97 children (aged 7-17 years; mean age ≈ 12), recruited from hospital emergency departments within one month of experiencing a single-incident trauma (e.g., motor vehicle accidents, dog bites, falls, assaults, house fires).

Inclusion criteria: exposure to a discrete traumatic event; admission to hospital for assessment or treatment.

Exclusion criteria: traumatic brain injury, ongoing maltreatment, or significant developmental delay.

Hitchcock et al. Methodology

Design: Prospective, longitudinal correlational study with assessments at 1 month and 6 months post-trauma.

Procedure:

At 1 month post-trauma, children completed:

The Child Posttraumatic Cognitions Inventory (CPTCI) to assess negative trauma-related appraisals.

The Clinician-Administered PTSD Scale for Children and Adolescents (CAPS-CA) to measure PTSD symptoms.

Questionnaires measuring perceived social support (child- and parent-reported).

At 6 months post-trauma, the CAPS-CA was re-administered to assess change or persistence in PTSD symptoms.

Analysis: Hierarchical regression and path analysis were used to assess the predictive relationship between early negative appraisals and later PTSD symptoms, and to test mediation by appraisals in the link between social support and PTSD.

Hitchcock et al. Results

Negative appraisals at 1 month significantly predicted PTSD symptom severity at 6 months, even after controlling for initial PTSD symptoms.

Children with more negative beliefs about the world, themselves, or the permanence of threat were more likely to have persistent or worsening PTSD symptoms.

Perceived social support (especially parent-reported) was negatively associated with negative appraisals.

Children with greater social support were less likely to form negative interpretations of the trauma.

Negative appraisals mediated the relationship between social support and PTSD: social support reduced negative appraisals, which in turn predicted lower PTSD severity.

Adaptive appraisals (e.g., beliefs about coping or resilience) were related to initial PTSD symptoms but not predictive of long-term outcomes.

Hitchcock et al. Significance

Strong support for Ehlers and Clark's (2000) model: children's cognitive interpretation of trauma, not just the trauma itself, shapes whether PTSD symptoms develop or persist.

Identifies negative appraisals as a cognitive mechanism linking social support to psychological outcomes.

Suggests that early interventions targeting maladaptive appraisals—such as through trauma-focused CBT—could reduce the risk of chronic PTSD in children.

Emphasizes the protective role of supportive social environments, including parental presence and validation, in buffering trauma-related stress.

Hitchcock et al. Ethical Considerations

Informed consent was obtained from both children and their parents or guardians.

Participation was voluntary, with the right to withdraw at any time.

Children were assessed by trained clinicians using validated tools appropriate for their age.

The study involved minimal risk, focusing only on interviews and questionnaires.

Psychological support and referrals were available if children or families experienced distress during the research process.

The study was approved by a hospital ethics board and complied with ethical standards for research with minors and trauma-exposed populations.

Urry et al. (2006)

Individual Differences in Emotion Regulation: The Role of the Prefrontal Cortex and Amygdala

Urry et al. Aim

To examine how individual differences in the ability to cognitively regulate negative emotion—specifically through reappraisal—relate to neural activity in the prefrontal cortex and amygdala.

The study tests the top-down model of emotion regulation, which suggests that prefrontal regions modulate subcortical emotion-generating areas (like the amygdala), especially during cognitive control strategies such as reappraisal.

Urry et al. Participants

N = 32 healthy adults, ages 35-55 (17 female).

Participants were recruited from a community sample as part of a larger longitudinal study on aging, affect, and health.

All participants had normal or corrected-to-normal vision and no history of neurological or psychiatric illness.

Urry et al. Methodology

Design: Correlational study using functional magnetic resonance imaging (fMRI).

Procedure:

Participants viewed negative and neutral images (drawn from the International Affective Picture System).

During each trial, they received one of two instructions:

Attend: Look at the image and allow themselves to respond naturally.

Reappraise: Use cognitive reappraisal to reinterpret the meaning of the negative image in a way that reduces its emotional impact (e.g., imagining the situation has a positive outcome or isn't real).

Brain activation was recorded using fMRI while participants engaged in the task.

After the fMRI scan, participants completed the Emotion Regulation Questionnaire (ERQ), a validated self-report measure that assesses individual differences in the habitual use of two emotion regulation strategies: reappraisal and suppression.

Key Brain Regions of Interest:

Amygdala: Associated with emotional salience, especially negative affect.

Prefrontal cortex (PFC), including:

Ventromedial PFC (vmPFC) – associated with valuation and regulation of emotional responses.

Dorsolateral PFC (dlPFC) – involved in working memory and cognitive control processes that support reappraisal.

Urry et al. Results

Individuals who reported greater habitual use of reappraisal on the ERQ showed:

More activation in vmPFC and dlPFC during the reappraisal condition.

Less activation in the amygdala, suggesting successful downregulation of negative emotion.

A negative correlation was found between vmPFC activity and amygdala activity:

As vmPFC activation increased, amygdala activation decreased—evidence supporting top-down emotion regulation.

Importantly, this relationship was found across individuals, indicating that people differ in how effectively their prefrontal regions can regulate emotional reactivity.

Urry et al. Significance

This study provides empirical support for the top-down model of emotion regulation, aligning with Gross's process model of emotion regulation, which posits that reappraisal occurs early in the emotion-generation process and involves cognitive control.

Shows that prefrontal cortical areas (especially vmPFC and dlPFC) play a key role in modulating emotional responses through reappraisal by inhibiting amygdala activity.

Offers neural evidence for why some individuals are better at managing negative emotions—habitual reappraisers show stronger engagement of brain areas involved in regulation and weaker responses in emotion-related subcortical regions.

Findings have broader implications for affective neuroscience, clinical psychology, and interventions aimed at improving emotion regulation (e.g., CBT, mindfulness)

Irish et al. (2011)

Gender Differences in PTSD Following Trauma Exposure

Irish et al. Aim

To investigate gender differences in the development of Post-Traumatic Stress Disorder (PTSD) following a traumatic event, with a specific focus on whether subjective appraisals (such as perceived threat and anxiety) explain why women are more likely to develop PTSD than men.

The study aimed to test cognitive and emotional factors that may mediate the gender-PTSD relationship.

Irish et al. Participants

N = 253 participants (124 males, 129 females), aged 18–50 years

All participants were hospitalized after experiencing a single traumatic event, such as a motor vehicle accident, industrial accident, or physical assault.

Participants were recruited within days of trauma exposure and followed for 6 months to assess the development of PTSD symptoms.

Irish et al. Methodology

PTSD symptoms were measured using the Clinician-Administered PTSD Scale (CAPS).

Subjective appraisals were assessed using self-report measures of:

Perceived life threat

Peritraumatic anxiety

Dissociation

Perceived social support

Objective severity of trauma was also assessed using injury records and medical ratings.

Analysis:

Statistical models examined gender as a predictor of PTSD symptom severity.

Mediation analysis tested whether cognitive-affective appraisals accounted for the gender difference.

Irish et al. Results

Women were significantly more likely than men to develop PTSD following trauma exposure, even after controlling for objective trauma severity.

Women reported higher levels of perceived life threat, greater peritraumatic anxiety, and more dissociation—all of which were significant predictors of later PTSD symptoms.

Perceived threat and anxiety partially mediated the relationship between gender and PTSD outcomes, suggesting that how individuals interpret and respond to trauma contributes to risk.

No significant gender differences were found in objective injury severity, indicating that subjective experiences, not physical harm, drove the disparity.

Irish et al. Significance

Supports the idea that subjective appraisals and affective responses to trauma (rather than the trauma itself) contribute to gender differences in PTSD.

Reinforces Ehlers & Clark’s cognitive model of PTSD, which emphasizes the role of trauma interpretations and emotional processing.

Findings contribute to trauma-informed clinical approaches by showing that early interventions should focus on:

Addressing perceived threat

Managing acute anxiety

Reducing dissociation

Highlights the importance of gender-sensitive assessment and early cognitive-emotional screening following trauma exposure.

Irish et al. Ethical Considerations

Informed consent was obtained from all participants, with special care due to their recent trauma exposure.

Participants were informed of their right to withdraw at any time.

Clinical referrals were offered to participants showing elevated PTSD symptoms or distress during the study.

The study involved no experimental manipulation—only structured interviews and questionnaires.

Ethical approval was granted by the affiliated hospital and university Institutional Review Boards (IRBs).

Data were anonymized and stored securely to protect confidentiality.

Garrison et al. (1995)

Racial and Ethnic Differences in PTSD Prevalence Among Adolescents

Garrison et al. Aim

To investigate whether racial and ethnic minority groups in the United States are more likely to develop Post-Traumatic Stress Disorder (PTSD) following trauma exposure, and to examine whether such differences remain after controlling for the type and severity of trauma.

The study sought to understand disparities in PTSD risk among African American, Hispanic, and White adolescents, with attention to cultural and socioeconomic factors that might shape trauma outcomes.

Garrison et al. Participants

N = 1,200 adolescents aged 11–17 from Florida, representing diverse racial and ethnic backgrounds:

African American, Hispanic, and White youth

Participants were selected as part of a larger epidemiological survey on adolescent mental health, using structured diagnostic interviews.

Garrison et al. Methodology

Design: Cross-sectional epidemiological survey with structured diagnostic assessments

Procedure:

Adolescents and their caregivers participated in interviews using the Diagnostic Interview Schedule for Children (DISC), which assesses psychiatric disorders according to DSM-III-R criteria.

The interview included questions about:

Exposure to potentially traumatic events

Symptoms of PTSD

Sociodemographic variables (race, gender, income, family structure)

Participants were classified as having PTSD if they met full DSM criteria.

Statistical analyses assessed whether PTSD prevalence differed by race/ethnicity, gender, and trauma type, and whether any differences persisted after adjusting for confounding variables.

Garrison et al. Results

African American and Hispanic adolescents were significantly more likely to meet criteria for PTSD than White adolescents.

These racial/ethnic disparities persisted even after controlling for type of trauma, trauma severity, and socioeconomic status.

Female adolescents also had a higher prevalence of PTSD than males, consistent with prior research.

Among trauma types, interpersonal violence (e.g., assault, abuse) was most strongly associated with PTSD, and minority youth reported higher rates of such experiences.

Racial/ethnic differences in PTSD were not explained solely by differences in trauma exposure, suggesting that post-trauma psychological and contextual factors (e.g., access to care, cultural norms, chronic stress) may contribute.

Garrison et al. Significance

This was one of the earliest large-scale studies to show that racial and ethnic minority youth in the U.S. are at greater risk for PTSD, even when exposed to similar types of trauma as White youth.

The findings suggest that systemic factors, such as chronic discrimination, poverty, community violence, and barriers to mental health care, may interact with trauma exposure to amplify PTSD risk in minority populations.

Supports a bio-psycho-social approach to PTSD that considers social determinants of health, including race and ethnicity.

Highlights the importance of culturally responsive assessment and treatment for trauma-exposed youth.

Garrison et al. Ethical Considerations

Informed consent and assent were obtained from both caregivers and adolescents.

Participants were informed of their right to withdraw and assured that their responses would be confidential.

Referral procedures were in place for adolescents who showed signs of distress or met diagnostic criteria.

The research adhered to ethical guidelines for studies with minors and with racial/ethnic minority populations, including sensitivity to issues of cultural identity and mental health stigma.

The study was approved by the appropriate institutional review boards (IRBs) and was part of a state-funded initiative on adolescent health.

Luby et al. (2013)

The Effects of Poverty on Childhood Brain Development: The Role of Caregiving and Stress

Luby et al. Aim

To examine whether poverty during early childhood is associated with changes in brain structure, particularly in the hippocampus and amygdala, and to determine whether these effects are mediated by caregiving quality and exposure to stressful life events.

The study sought to test the hypothesis that socioeconomic status (SES) influences neurodevelopment through environmental mechanisms that impact stress regulation and emotional development.

Luby et al. Participants

145 children, initially aged 3 to 6 years, recruited from a longitudinal study on preschool depression and brain development.

The sample included children from a wide range of socioeconomic backgrounds, ensuring variation in family income and parental education.

Participants were followed over time and underwent MRI scans around age 10.

Luby et al. Methodology

Design: Longitudinal correlational study with behavioral observations and neuroimaging.

Procedure:

At study entry (preschool age):

Families were assessed for income-to-needs ratio (a standardized SES index).

Parent-child interactions were directly observed and rated for caregiving supportiveness (e.g., warmth, responsiveness).

Parents reported on the child’s exposure to stressful life events (e.g., death, violence, financial strain).

At follow-up (around age 10), children underwent MRI scans to measure volumes of:

Hippocampus

Amygdala

Total gray matter

Analysis:

Multiple regression and mediation models tested whether SES predicted brain volumes directly and whether caregiving quality or stress exposure mediated the relationship.

Luby et al. Results

Lower socioeconomic status in early childhood was significantly associated with:

Smaller hippocampal volumes

Reduced total gray matter volume

No direct SES effect was observed on amygdala volume, though stress exposure predicted amygdala differences in secondary analyses.

Caregiving quality and stressful life events were significant mediators:

-Supportive caregiving was associated with larger hippocampal volume, even in low-SES contexts.

-Exposure to stressful life events partially explained the link between poverty and reduced hippocampal size.

The findings were independent of psychiatric symptoms, suggesting that environmental adversity, not mental illness, accounted for the neural differences.

Luby et al. Significance

Demonstrates that poverty is linked to neurodevelopmental changes, especially in brain regions involved in memory, learning, and stress regulation (hippocampus).

Provides neuroscientific evidence that early caregiving and chronic stress are modifiable environmental factors influencing brain development in children from low-income families.

Emphasizes the plasticity of the developing brain—supportive environments may buffer the negative effects of poverty.

Has strong implications for public health and policy, supporting early intervention programs (e.g., parenting support, early childhood education) that promote emotional and cognitive development in disadvantaged populations.

Luby et al. Ethical Considerations

Informed consent was obtained from all parents/guardians; children gave age-appropriate assent.

All procedures were reviewed and approved by the university’s Institutional Review Board (IRB).

Participation was voluntary, and families were offered compensation for their time and transportation.

Psychological support and referrals were available for any family expressing emotional or mental health concerns.

MRI procedures were conducted using child-friendly protocols to reduce anxiety and discomfort.