Table 2

Numbers needed to treat in placebo-controlled trials in mania

Treatment group (reference) Treatment n Duration (weeks) Criterion of response Dropouts due to inefficacy (%) Dropouts due to adverse events, etc. (%) Response (%) Absolute risk reduction (%) NNT1
n 95% CI
SADS-M, Schedule for Affective Disorders and Schizophrenia-Mania; YMRS, Young Mania Rating Scale.
1.The number needed to treat (NNT) is calculated by dividing the absolute risk reduction into 100 and correcting to the next highest integer. It represents the number of patients who must be treated for one patient to achieve a response as a result of the drug.
Monotherapy Olanzapine 70 3 50% less YMRS 29 0 49 25 4 3-10
(Tohen et al, 1999) Placebo 64 48 3 24
Monotherapy Valproate 68 3 50% less, SADS-M 30 6 48 23 5 3-14
(Bowden et al, 1994) Placebo 73 51 3 25
Lithium 35 33 11 49 24 5 3-22
Combination with mood stabiliser Risperidone 75 3 50% less YMRS 39 59 17 6 4-82
(Yatham, 2000) Placebo 75 55 42
Combination with mood stabiliser Olanzapine 229 6 50% less YMRS 4 28 68 23 5 3-9
(Tohen et al, 2000) Placebo 115 13 18 45
Combination with antipsychotic Valproate 69 3 50% less YMRS 1 9 70 24 5 3-13
(Muller-Oerlinghausen et al, 2000) Placebo 67 3 13 46