Classification and Subtypes of Affective Disorders

1. Overview & Epidemiology

Core definitions (Gajdos lecture):

• Mood = a pervasive and sustained feeling tone, experienced internally, that colours the person's behaviour and perception of the world.
• Affect = the external expression of mood (what the examiner observes).
• Sadness / grief are NOT depression — they are normal reactions to loss; grief is culturally shaped and only sometimes pathological.

The fundamental split (memorise this first):

• Unipolar = patient has only major depressive episodes → Major Depressive Disorder.
• Bipolar = patient has manic episodes (alone or with depressive episodes), or hypomanic + depressive episodes.
• Three "in-between" categories named in the lecture: hypomania, cyclothymia, dysthymia (sub-syndromal / chronic low-grade forms).

DSM-5-TR splits the old "mood disorders" chapter into two adjacent chapters:

• Bipolar and Related Disorders: Bipolar I, Bipolar II, Cyclothymic disorder, substance/medication-induced, due to another medical condition.
• Depressive Disorders: Major Depressive Disorder (MDD), Persistent Depressive Disorder (dysthymia), Disruptive Mood Dysregulation Disorder, Premenstrual Dysphoric Disorder, substance/medication-induced, due to another medical condition.

Gajdos epidemiology pearls: yearly incidence of major depression ≈ 1.59% (women 1.89%, men 1.10%); annual incidence of bipolar illness <1%. MDD clusters in people without close interpersonal relationships / divorced / separated.

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