Table 1.

Comparison of study sample sizes, depression outcome variables, depression severities and numbers needed to treat

Study	N	Depression outcome variable	Depression severity	NNT
IMPACT	1,801	Hopkins symptom checklist-20	Major depression or dysthymia	At 12 months = 4α At 18 months = 6α At 24 months = 9α
PROSPECT	598	Hamilton depression Rating Scale	Major or minor depression	At 24 months = 6α
MANAS	2,796	Clinical Interview Schedule-Revised	Major depression	At 6 months = 8β

N = number of randomized participants. NNT = Number needed to treat.

^αTreatment response was defined as a 50% reduction in depression outcome variable score.

^βBased on overall primary outcome: recovery from common mental disorders including depression via ICD-10.