Lecture Notes: Understanding Major Depressive Disorder

Introduction to Depression

• Depression: A mental state of low mood.
• Major Depressive Disorder (MDD): Most commonly referred subtype.
• Predicted to be the leading cause of disease burden worldwide by 2030.

Historical Context

• Term "Major Depressive Disorder" first used in the 1970s.
• Added to the DSM (Diagnostic and Statistical Manual of Mental Disorders) in the 1980s.
• Current version is DSM-5, which outlines 9 diagnostic criteria.

Diagnostic Criteria (DSM-5)

• Core Symptoms:
  • Low mood most of the day, most days.
  • Anedonia: Loss of pleasure or interest.
• Additional Symptoms:
  • Significant weight changes.
  • Sleep disturbances (insomnia or hypersomnia).
  • Fatigue or loss of energy.
  • Psychomotor retardation.
  • Feelings of guilt or worthlessness.
  • Concentration difficulties.
  • Recurrent thoughts of death.
• Diagnosis requires:
  • Five or more symptoms over at least two weeks.
  • Significant distress or impaired functioning.
  • Symptoms not due to substance use/another condition.

Causes of Major Depressive Disorder

• Genetic Factors:
  • Genetics account for 40% of risk differences.
  • High concordance in monozygotic twins.
  • Family history is a risk factor.
• Environmental Factors:
  • Stressful life events, childhood abuse correlate with severity.
  • Presence of other medical conditions or substance abuse.

Theories and Models

• Diathesis-Stress Model: Stress on a pre-existing vulnerability increases the likelihood of depression.
• Monoamine Theory: Lack of neurotransmitters like serotonin, dopamine.
• Other Theories:
  • Abnormalities in hypothalamic-pituitary axis.
  • High cortisol levels and less dexamethasone suppression.
  • Link with thyroid and growth hormone levels.
  • Immune system abnormalities (cytokine release).

Epidemiology

• Lifetime risk: ~12% (1 in 8).
• Twice as common in females.
• Mean age of onset: 40 years.
• Increasing prevalence in younger individuals.

Diagnosis and Comorbidities

• ICD-11: Used in Europe.
• Severity measured by Patient Health Questionnaire 9.
• Common comorbid disorders: Anxiety, substance misuse, ADHD, PTSD, chronic pain.

Treatment Approaches

• Lifestyle Modifications:
  • Exercise, healthy diet, regular schedule.
  • Limiting alcohol, stopping drug use.
• Psychotherapy:
  • Cognitive Behavioral Therapy, Interpersonal Therapy.
  • First line for under 18s (NICE guidelines).
• Pharmacological Therapy:
  • SSRIs (e.g., Sertraline, Citalopram).
  • SNRIs (e.g., Duloxetine, Venlafaxine).
  • Atypical antidepressants (e.g., Metazepine).
  • Tricyclics and MAOIs (less common).
  • Vitamin D supplementation, COX-2 inhibitors.
• Electroconvulsive Therapy (ECT):
  • Effective for treatment-resistant MDD.
  • Involves induced seizures, administered under anesthesia.
  • 50% effectiveness, with 50% relapse in 12 months.