Objective: To assess the antidepressant efficacy of S-adenosyl methionine (SAMe), a naturally occurring methyl donor, versus the selective serotonin reuptake inhibitor (SSRI) escitalopram and a placebo control; and to determine whether serum histamine or carnitine levels modified treatment response.
Methods: We examined a subsample (n=144) from one site of a two-site study of adults with diagnosed Major Depressive Disorder (MDD), recruited from 4/13/05 to 12/22/09, who consented to the additional blood draw for serum histamine and carnitine levels. After washout, eligible subjects were randomized to SAMe (1600-3200mg/daily), escitalopram (10-20mg/daily), or matching placebo for 12 weeks of double-blind treatment (titration at week 6 in non-response).
Results: On the primary outcome of the Hamilton Depression Rating Scale (HAMD-17), a significant difference in improvement was observed between groups from baseline to week 12 (p=0.039). The effect size from baseline to endpoint was moderate to large for SAMe versus placebo (d=0.74). SAMe was superior to placebo from week 1, and to escitalopram during weeks 2, 4, and 6. No significant effect was found between escitalopram and placebo or SAMe. Response rates (HAMD-17≥50% reduction) at endpoint were 45%, 31%, and 26% for SAMe, escitalopram, and placebo, respectively; while remission rates (HAM-D≤7) were 34% for SAMe (p=0.003), 23% for escitalopram (p=0.023), and 6% for placebo. No correlation between baseline histamine level and reduction of HAMD-17 score was found for either the SAMe or escitalopram groups. Baseline carnitine levels were also not found to moderate response to either treatment.
Limitations: While SAMe appears to be an effective antidepressant agent, the overall findings from the parent study (which showed no significant difference between groups due to site differences) must be taken into consideration.
Conclusions: These preliminary results provide encouraging evidence for the use of SAMe in the treatment of MDD. Histamine and carnitine serum level may not necessarily moderate response to SAMe.
Keywords: Carnitine; Depression; Histamine; One-carbon cycle; RCT; S-adenosyl methionine.
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