中文摘要：

早发性抑郁的发病机制尚不明确。现仅有选择性5-HT重摄取抑制剂（ selective serotonin reuptake inhibitors, SS-RIs） SSRIs批准用于临床治疗早发性抑郁,显示出五羟色胺（5-hydroxytryptamine/serotonin,5-HT）5-HT是早发性抑郁发病机制中最重要的神经递质。目前有关中枢5-HT能系统在早发性抑郁中的作用研究主要集中在5-HT合成不足、5-HT运输功能障碍等方面,并与5-HT能系统较早发育成熟有关。色氨酸吸收障碍以及5-HT合成障碍都会导致5-HT合成不足；同时,5-HT转运体蛋白（5-HTT ）基因多态性位点5-HT-TLPR低转录效率基因型可能会增加早发性抑郁的患病风险。为进一步理解中枢5-HT能系统在早发性抑郁中的作用,未来需要进行更广泛更深入的基础及临床研究。

英文摘要：

Nowadays the pathogenesis of early-onset depression is still uncertain. Only SSRIs are currently approved for clinical use as antidepressants in children and adolescents, indicating that 5-HT is the most important neurotransmitter involved in the dis-ease. Current studies with regard to central 5-HTergic system in early-onset depression mainly focus on 5-HT synthesis deficien-cy, 5-HT transportation dysregulation, as well as the earlier mat-uration of 5-HT system than norepinephrine system. 5-HT precur-sor tryptophan malabsorption and dysregulation of 5-HT synthesis can contribute to 5-HT deficiency. Moreover, the 5-HTTLPR low-expressing genotypes may increase the risk of early-onset de-pression. It is necessary to make preclinical and clinical studies more widely and deeply about the effect of central 5-HTergic sys-tem in early-onset depression in future.