MBC works.
Here's why.

A thermometer doesn't turn illness into a number. It makes the invisible — visible. PHQ-9 doesn't describe a person. It tracks which direction their condition is moving over the past two weeks. All interpretation is yours. MBC doesn't take away judgment. It gives it more material to work with.

This happens without questionnaires too — in every session, every time a client says 'everything's fine.' Data doesn't solve social desirability, but makes it visible: the discrepancy between what a client says in conversation and what they mark on a scale — is itself a clinically significant signal for discussion. Not a trap. An entry into therapeutic conversation.

A fair point for many interventions. Less fair for MBC. Studies in naturalistic settings reproduce results: Miller et al. (2006) showed similar improvements in private practice, not lab conditions. MBC isn't a treatment protocol — it's a feedback system. It improves what you already do, rather than replacing it.

PHQ-9 takes 2–3 minutes. The client fills it out before the session. You open the meeting with a ready picture — instead of spending the first 10 minutes on 'how was your week.' Research shows: MBC doesn't add time to sessions. It redistributes it in favor of work, not reconnaissance.

This is the most honest question. And the most important. Without data, you also don't know if you're effective — you just don't see the reverse. MBC doesn't create the problem. It makes an existing problem visible — early enough to do something about it. A clinician afraid to look at data has already made a decision about its contents.