I wouldn't call this a minor detail (i.e., nitpicking), and it is worth pointing out again and again when these studies get public attention.
We should encourage stronger research designs (including A/B tests) if we care about the impact of AI use on mental health outcomes. A study like this one cannot say anything about the effect at all (it is even possible that AI use will have a positive impact on mental health).
We should encourage stronger research designs (including A/B tests) if we care about the impact of AI use on mental health outcomes. A study like this one cannot say anything about the effect at all (it is even possible that AI use will have a positive impact on mental health).