Table 1 Derivation of depression variables [37]

1. Ever felt depressed for a whole week

2. Ever disinterested or unenthusiastic for a whole week

3. Only 1 episode

4. ≥ 2 episodes

5. Episode lasted ≥2 weeks

6. Ever seen a GP for nerves, anxiety, tension or depression

7. Ever seen a psychiatrist for nerves, anxiety, tension or depression

Single episode of probable major depression

{(1) AND (3) AND (5) AND [(6) OR (7)]}

OR

{(2) AND (3) AND (5) AND [(6) OR (7)]}

Probable recurrent major depression (moderate)

[(1) OR (2)] AND (4) AND (5) AND (6)

Probable recurrent major depression (severe)

[(1) OR (2)] AND (4) AND (5) AND (7)