lecture 21: Post-Traumatic Stress Disorder (PTSD)

Post-Traumatic Stress Disorder (PTSD)

Learning Objectives

  • Describe the acute stress response (SAM and HPA): Understanding the two systems activated during a stress response is crucial for recognizing how PTSD develops.

  • Discuss the negative consequences of chronic stress on brain structure: Chronic stress has significant impacts on brain regions important for emotional regulation.

  • List the primary symptoms required for a diagnosis of PTSD: Knowledge of symptoms aids in understanding the disorder.

  • Describe the process and neurobiology of extinction learning: Extinction learning is essential for understanding how fear responses can diminish over time.

  • Describe the 3 R’s of extinction memory: Exploring concepts related to fear and extinction memory can inform treatment approaches.

  • What are 3 ways extinguished fear can return? Recognizing triggers for the return of fear can help in therapy.

  • Draw parallels between fear memory and PTSD: Understanding the cognitive processes involved in PTSD through the lens of fear memory can enhance comprehension and intervention strategies.

Defining PTSD

  • PTSD as a Disorder: PTSD is categorized as a stress and learning disorder.

  • DSM-5 Classification: As per the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5), PTSD falls under the category of Trauma- and Stressor-related Disorders, which includes:

    • Post-Traumatic Stress Disorder (PTSD)

    • Acute Stress Disorder

    • Adjustment Disorders

    • Prolonged Grief Disorder

  • Traumatic Event Requirement: A qualifying event must have occurred for PTSD diagnosis, where symptoms notably affect memory.

Understanding Stress

  • Definition of Stress: Stress refers to any circumstance that disrupts the body's homeostatic balance, which may include:

    • Starvation

    • Fear

    • Severe insomnia

    • Social isolation

    • Parental neglect

    • Physical and emotional abuse

    • Exposure to toxins or microbial infections

  • Adaptive Responses: The brain develops systems to activate adaptive responses to stressors and ultimately restore homeostasis.

Acute Stress Response

  • SAM and HPA Systems:

    • Sympathetic-Adrenal-Medullary (SAM) System: Activates quickly.

    • Hypothalamic-Pituitary-Adrenal (HPA) Axis: Activates more slowly.

  • Amygdala's Role: It is a critical brain region in activating the stress response and managing emotional responses to fear-inducing stimuli.

Effects of Stress on Memory

  • Consolidation of Emotional Memories: Stress enhances memory consolidation regarding emotional events regardless of whether they are positive or negative.

  • Functions of the Amygdala:

    • Mobilizes the body's defensive systems in response to threat.

    • Contributes to fear learning.

  • HPA Axis: Plays a crucial role in stress regulation, and the hippocampus is vital for maintaining this regulation. A disrupted negative feedback loop in stress response is linked to neuropsychiatric disorders.

Chronic Stress and Its Consequences

  • Effects of Chronic Stress:

    • Chronic activation of the stress response leads to long-term physiological and psychological consequences.

    • Areas of the brain related to emotional regulation and recovery become altered due to elevated stress hormones.

  • Changes in Brain Structure:

    • Amygdala Neurons: Increase in size after prolonged stress (Vyas et al., 2002).

    • Prefrontal & Hippocampal Neurons: Shrinkage occurs with chronic stress (McEwen & Morrison, 2013).

PTSD Prevalence and Risk Factors

  • Prevalence of PTSD:

    • Approximately 8% of individuals will develop PTSD.

    • An estimated 30% of those who experience a traumatic event will develop PTSD:

    • This rate is about 30% among Vietnam veterans.

    • Ranges from 10% to 15% in Gulf War veterans.

  • Risk Factors: Factors that increase the likelihood of developing PTSD include:

    • Experiencing dangerous events and traumas, particularly repeatedly.

    • Suffering injuries or witnessing injury/death.

    • Childhood trauma exposure.

    • Feelings of horror or extreme fear.

    • Lack of social support post-event.

    • Experiencing additional stress after the event, such as the death of a loved one or job loss.

    • History of mental illness or substance abuse.

Diagnostic Criteria for PTSD (DSM-5)

  1. Exposure to Trauma: Individuals must have experienced or been directly exposed to trauma.

  2. Re-experiencing Symptoms: This includes:

    • Intrusive memories

    • Traumatic nightmares

    • Prolonged physiological responses to trauma reminders

  3. Avoidance Symptoms: Behavioral avoidance related to reminders of trauma.

  4. Negative Changes in Mood and Cognition:

    • Inability to recall important aspects of the trauma.

    • Persistent negative beliefs about oneself or the world (e.g., feelings of anger, guilt, alienation).

    • Depressive symptoms.

  5. Changes in Arousal and Reactivity: Experiences may include hypervigilance, exaggerated startle response, sleep issues, difficulty concentrating, and irritability.

Insights from Fear Learning about PTSD

  • Fear Learning Mechanisms:

    • Includes classical conditioning: the pairing of an auditory conditioned stimulus (CS) with an unconditioned stimulus (UCS).

    • Contextual memory emphasizes the distinction between trauma (which is conditioned) and aversive scenarios (which are associated but not traumatic).

  • Persistent Memory Formation: Fear responses and avoidance behaviors can persist years after the original trauma, connecting back to the concepts of exaggerated fear response and poor control over fear.

Fear Extinction Process

  • Definition of Fear Extinction: Refers to the process of diminishing behavioral responses to threat-associated cues through repeated exposure without aversive stimuli (CS without UCS).

  • Competing Memories: Successful extinction creates new memories that compete with the original fear memory.

Return of Fear: The 3 R’s

  • Spontaneous Recovery: The re-emergence of fear after a period of time.

  • Renewal: The reinstatement of fear when the context changes from the extinction environment.

  • Reinstatement: The return of fear following reminders of the aversive experiences, such as a brief reminder of the trauma.

Neural Basis for Fear Extinction

  • Brain Regions Involved:

    • Prefrontal Cortex: Central to extinction learning, including top-down suppression of emotional reactions.

    • Hippocampus: Related to contextual learning, linked to the renewal of fear.

    • Amygdala: Involved in fear learning and extinction processes.

Characteristics of Extinction Memory

  • Extinction memory requires the prefrontal cortex for regulation and learning of context-specific responses.

  • Influence of Context: The conditions in which training occurs versus testing back might lead to differences in fear levels.

Broader Relevance of Extinction Learning

  • Extinction is not limited to fear: Associations can also be extinguished beyond just fear conditioning (CS-UCS to CS-no UCS).

  • Three R’s Applicability: Similar mechanisms apply across various forms of associative learning, leading to practical applications in drug addiction and other areas.

PTSD and Fear Memory Dynamics

  • Concerns about Control: Factors in PTSD share characteristics with fear memory behavior, showcasing poor control over fear as a common element.

Neurobiological Markers in PTSD

  • Prefrontal Cortex Activity: A decrease in activity has been observed in PTSD patients during tasks involving traumatic imagery (Arch Gen Psychiatry, 2004).

  • Amygdala and PFC Relationship: Evidence suggests disrupted interactions between the amygdala and prefrontal cortex.

  • Hippocampal Volume: Studies indicate reduced hippocampal volume may contribute to memory issues in PTSD, with genetic vulnerabilities further complicating these aspects.

Treatments for PTSD

  • Goal of Treatment: To mitigate arousal and stress-related symptoms.

  • Pharmacological Treatments:

    • Antidepressants such as SSRIs and SNRIs.

  • Psychotherapeutic Approaches:

    • Cognitive Behavioral Therapy (CBT) which includes:

    • Cognitive interventions challenging anxiety-inducing beliefs.

    • Behavioral components promoting exposure and extinction.

  • Challenges: Effective therapies must address the three R’s (spontaneous recovery, renewal, reinstatement) since extinction results in a new memory that co-exists with the original fear memory.

Future Directions of Research

  • Continued Investigation: There's a need for comprehensive research into complex PTSD formulations and the neurobiology underlying these experiences (Nees, Witt, & Flor, 2018).