The 30-minute mark functions as a qualifying threshold, not a dial to turn up. Once users cross it, mood improvement the next day is large and consistent, but coaching longer than 30 minutes didn't produce a proportionally larger effect. For operators and HR leaders, that reframes "engagement" away from maximizing minutes and toward simply getting users to a meaningful first session.

An exploratory secondary finding: across the most common day-1 mood states, users presenting as "drained" showed the smallest next-day improvement, a signal (not yet confirmatory) that fatigue-driven states may need a different intervention design than acute stress or sadness.