In addition, studies by Zhou et al. showed that carotenoids, including astaxanthin and zeaxanthin, downregulate IL-6 and IL-1β in the hippocampus and protect neurons from hyperglycemic damage, implicating that depression can be prevented by astaxanthin and zeaxanthin through the inhibition of hippocampal inflammation in diabetic mice (Zhou et al., 2017; Zhou et al., 2018). This evidence concerns the gene IL6 and major depressive disorder.