That's nearly a 15% reduction! It's also comparable to reductions seen in CFS (though CFS was per weight rather than per surface area, they should be comparable metrics). However, this is in comparison to bipolar, who themselves probably lack normal blood volume, so it's possible schizophrenia is a more extreme version of CFS where the blood volume is radically reduced. Will need more studies.

I notice the standard deviation is low for their sample size. Normally smaller sample sizes increase SD. However, comparing to a study with 30 subject per group, we can see the expected SD for blood volume (ml/kg) in this sample size of 20 should be greater than ±22.

The reason for this small SD is probably that subjects with ME/CFS are scrunched up against the lower end of the curve. The body simply will not allow blood volumes below a certain level. Judging by this study, I'd say around 50 ml/kg is the lowest possible number.

If this holds true, I'd expect rapid blood volume expansion from thyroid hormone. I'm also interested in whether thyroid hormone stimulates the production of albumin, given its anabolic properties.

If the mechanism is really the same as alpha blockers, then the blood volume expansion may be expected to be similar in constitution. However, I would expect more red blood cells in thyroid mediated volume expansion compared to alpha blockers. The reason, obviously, is because of the increased oxygen demand from thyroid hormone.