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PY0547_Week 11_Depression_ES_forBB

Introduction

  • Course: PYO547 Psychobiology I

  • Instructor: Dr. Ellen Smith

  • Focus: Biological basis of Depression

Sensitive Topics

  • Discussion of sensitive topics, including:

    • Low mood

    • Suicide

  • Students feeling unsettled should opt for alternative activities and seek support if needed.

Definition of Depression

  • Long-lasting negative affect (negative hedonic feelings)

  • Associated feelings: powerlessness, lack of motivation, inability to influence events (Beck, 1967)

Prevalence of Depression

  • Affects over 280 million people worldwide (WHO, 2023)

  • Leading cause of disability (WHO, 2020)

  • Gender disparity: Women are twice as likely to suffer from depression compared to men (Girguis & Yang, 2015)

  • Severe cases can lead to suicide, with over 700,000 deaths annually. It is the third leading cause of death in individuals aged 15-29 (WHO, 2024).

Lecture Overview

  • Topics to cover:

    • Terms & Symptoms of Depression

    • Causes (Biological, Environmental & Psychological Models)

    • Treatments (Pharmacological & Non-pharmacological)

    • Optional learning activities

Terms and Symptoms

Types of Mood Disorders

  • Unipolar Depression: Prolonged sadness and despondency.

  • Bipolar Depression: Alternating periods of depression and mania.

  • Dysthymia (Persistent Depressive Disorder): Milder, long-lasting version of major depression.

  • Cyclothymia: Milder, long-lasting bipolar disorder version.

Symptoms of Major Depressive Disorder (MDD)

Emotional Symptoms

  • Sadness, tearfulness, misery

  • Low self-esteem, helplessness

Cognitive Symptoms

  • Rumination, perception issues, attentional difficulties

  • Memory problems

Motivational Symptoms

  • Energy loss, decreased goal-oriented behavior

Physical Symptoms

  • Sleep disturbance, appetite loss, aches and pains

  • Loss of libido, weight changes

Biological Models of Depression

Monoamine Hypothesis

  • Proposed by Joseph Schildkraut, based on initial findings regarding neurotransmitters.

Key Neurotransmitters

  • Monoamines include serotonin, norepinephrine, and dopamine.

    • Evidence:

      • Anti-hypertension drug (reserpine) depletion leads to depression.

      • Anti-tuberculosis drug (iproniazid) boosts monoamine levels, alleviating depression.

  • This hypothesis spawned the first antidepressants and is sometimes called the neurotransmission hypothesis.

Mechanism of Action (Normal vs. Depressed)

Non-depressed State

  • Efficient synthesis and transport of monoamines.

  • Monoamines bind effectively to post-synaptic receptors for signal transmission.

Depressed State

  • Inefficient synthesis and re-absorption of monoamines leading to insufficient levels for binding at post-synaptic neurons.

Anti-depressant Treatments

  • Aim to increase monoamine availability in the synapse through:

    • Blocking reabsorption (SSRIs)

    • Inhibiting monoamine-degrading enzymes (e.g., Monoamine Oxidase inhibitors)

Critiques of the Monoamine Hypothesis

  • Cannot fully explain treatment-resistant depression, as up to 30% do not respond to standard treatment.

  • Latency period (2-6 weeks) for response is unexplained.

  • The hypothesis is considered overly simplistic.

Neuroplasticity Theory

  • Focuses on reduced neuroplasticity leading to neuron loss and lower neurotrophin synthesis (e.g., BDNF).

  • Neuroplasticity refers to the brain's ability to reorganize itself and form new neural connections.

Evidence Support

  • Decreased neuroplasticity observed in hippocampus and PFC of depressed patients.

  • Antidepressants may improve neuroplasticity and increase concentrations of neurotrophic factors.

Stress and Depression

  • Major depressive episodes correlate with an increase in stressful life events (Hammen, 2005).

  • The Hypothalamus-Pituitary-Adrenal-Axis (HPA) response is crucial in understanding the biological mechanisms.

Chronic Stress Effects

  • Prolonged elevation of cortisol from chronic stress is neurotoxic, affecting hippocampal neurons and functionality.

  • A vicious cycle occurs with continued stress exacerbating structural and functional deficits.

Neurotransmitter Interaction

  • Chronic stress dysregulates stress hormone systems, altering neurotransmitter balances and potentially leading to depression.

Gene-Environment Models of Depression

Twin Studies

  • Bierut et al. (1999): Examined monozygotic and dizygotic twins for major depression correlation, highlighting genetic and environmental influences.

Gene-Environment Interactions

  • Caspi et al. (2003): Identified that individuals with short serotonin transporter genes have increased depression risk under stress, contrasting with those with variant responses.

  • Stressful events interplay with genetic predispositions to modulate depression risk.

Resilience Factor

  • Wingo et al. (2010) indicates that resilience can mitigate depression severity related to childhood trauma.

Psychological & Environmental Factors

Psychological Processing Biases

  • Depressed individuals tend to focus on negative information, affecting their cognitive processing and emotional responses.

Environmental Triggers

  • Factors such as single parenthood and unemployment increase depression risk. Odds ratios help assess these associations with outcomes.

Treatments for Depression

Pharmacological Treatments

  • SSRIs enhance monoamine availability by blocking reabsorption or inhibiting breakdown enzymes.

Non-Pharmacological Treatments

  • Comparatively effective outcomes between drugs, cognitive behavioral therapy (CBT), or their combination (Amik et al., 2015).

    • Psychological Therapies Include:

      • Cognitive Behavioral Therapy

      • Interpersonal therapy

      • Other therapeutic approaches

Conclusion

  • Covered:

    • Types and symptoms of depression

    • Biological, environmental, social, and psychological explanations

    • Treatments (both pharmacological and non-pharmacological)

    • Emphasis on mental health care alongside physical health.

Resources and Support Links

  • Various links for mental health support, counseling, workshops, and self-help resources.

Essential Reading

  • A selection of key readings and further resources regarding the biological and environmental underpinnings of depression.