This is a direct quote from
Latuda Dosage Guide - Drugs.com under the section for Latuda for bipolar disorder depression treatment:
"
LATUDA has been shown to be effective in a dose range of 20 mg per day to 120 mg per day as monotherapy or as adjunctive therapy with lithium or valproate [see Clinical Studies (14.2)]. The maximum recommended dose, as monotherapy or as adjunctive therapy with lithium or valproate, is 120 mg per day. In the monotherapy study, the higher dose range (80 mg to 120 mg per day) did not provide additional efficacy, on average, compared to the lower dose range (20 to 60 mg per day) [see Clinical Studies (14.2)]."
I wouldn't be concerned about the last sentence above. What works for your friend works for them.