4.2 — Mood (Affective) Disorders

2026 📋 Syllabus Objectives

By the end of these notes, you should be able to:

  1. Describe the diagnostic criteria for depressive disorder (unipolar depression) and bipolar disorder, and explain the Beck Depression Inventory (BDI)
  2. Explain biological (biochemical and genetic — Oruč et al., 1997) and psychological (Beck's cognitive theory and learned helplessness) explanations for mood disorders
  3. Describe and evaluate treatments: biological (antidepressants) and psychological (Beck's cognitive restructuring and Ellis's REBT)

📖 SECTION 1 — Diagnostic Criteria

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What are Mood (Affective) Disorders?

Mood disorders — also called affective disorders — are mental health conditions where a person's mood (how they feel emotionally) is severely disrupted for long periods of time. "Affective" simply means "related to emotions or feelings." The two main mood disorders you need to know are depressive disorder (unipolar depression) and bipolar disorder.

1.1 Depressive Disorder (Unipolar Depression)

The word "unipolar" means the person's mood is stuck at only one extreme — the low extreme. Think of it like a dial that only turns in one direction: downward.

To be diagnosed with depressive disorder, a person must show a number of specific symptoms that have been present for at least two weeks. These symptoms fall into two groups:

Core (main) symptoms — at least one must be present:

  • Persistent low mood — feeling deeply sad, empty, or hopeless nearly every day
  • Loss of interest or pleasure (called anhedonia) — no longer enjoying activities that used to bring happiness (e.g., hobbies, socialising, food)

Additional symptoms — enough must be present to make a total of at least 5 symptoms overall:

  • Significant change in weight or appetite (eating much more or much less than usual)
  • Sleep problems — sleeping too much (hypersomnia) or not enough (insomnia)
  • Fatigue — feeling exhausted and having very little energy
  • Feelings of worthlessness or excessive guilt
  • Difficulty concentrating or making decisions
  • Psychomotor changes — moving or speaking much more slowly than normal, or feeling very restless and agitated
  • Recurrent thoughts of death or suicide

💡 Simple summary: Unipolar depression = persistent low mood + several other emotional, physical, and thinking-related problems, lasting at least 2 weeks.

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