> If an intervention only 'works' because of the placebo effect, than that intervention doesn't actually work and there is no reason for someone else to use it.

Absence of proof doesn't mean proof of absence. So it may or may not be placebo, but it's an interesting data point for me (just bought blue blocker glasses, plan to try out. At $15-20 per, it's a no-brainer even if it doesn't work out).