The NNT[1] of Prozac, and SSRIs in general, has been previously estimated around 6. Meaning that treatment is more helpful than a sugar pill in only 1 out of 6 cases (a dirty secret).

Meanwhile the NNH[2] is as low as 21, that is 1 in 21 cases will stop due to negative side effects.

Source: https://www.aafp.org/pubs/afp/issues/2008/0315/p785.html

[1]Number Need to Treat, that is, number of patients you need to treat to prevent one additional bad outcome

[2]Number Needed to Harm, that is, number of patients you need to treat to generate side effects so bad that someone halts treatment