Table 1.

Association of plasma serotonin concentrations with clinical outcomes.

Plasma Serotonin	Clinical Outcome	Remission at 4 wks	Remission at 8 wks	Response at 4 wks	Response at 8 wks	% change at 4wks	% change at 8wks
Baseline		p = 0.012 OR = 1.41	p = 0.028 OR = 1.31	p = 0.007 OR = 1.40	p = 0.047 OR = 1.30	p = 0.015 r = −0.14	p = 0.019 −0.14
Change after 4 weeks		p = 0.011 OR = 1.40	p = 0.041 OR = 1.27	p = 0.026 OR = 1.31	p = 0.060 OR = 1.27	p = 0.021 r = −0.13	p = 0.024 r = −0.13
Change after 8 weeks		p = 0.069 OR =1.27	p = 0.147 OR = 1.19	p = 0.037 OR = 1.29	p = 0.130 OR = 1.21	p = 0.041 r = −0.12	p = 0.06 r = −0.11

Plasma serotonin concentrations at baseline and decreases in plasma serotonin concentrations after four weeks of SSRI treatment were nominally associated with remission, response, and percent change in QIDS-C16 score. The decrease in plasma serotonin between baseline and eight weeks of SSRI treatment was associated only with the response at four weeks and percent change in QIDS-C16 at four weeks. OR > 1 indicates improvement (associated with higher baseline and larger changes in plasma serotonin concentrations) and the negative r values indicate a decrease in QIDS-C16 scores, ie: improvement. P-values < 0.05 have been bolded.