It's not a very conclusive study for the reasons you mention. Researchers have long suspected connections between DMT and NDEs (see my other comments), but the

It's not a very conclusive study for the reasons you mention. Researchers have long suspected connections between DMT and NDEs (see my other comments), but the bottleneck here is that it's still so difficult to get funding and approval to do studies with these substances (it was actually not possible at all for decades) that this is about the state-of-the-art. Hopefully this is now changing and things will progress, in the meantime this is better than nothing, perhaps unless taken out of proportion! Disclaimer: I just follow this field and have no credentials in it.