1.Introduction
Menopause
is generally defined as the ”cessation” of menstruation for 12
consecutive months and is considered as the end of a woman’s
reproductive life1.
During this period, women always
experience many metals distresses, such as poor concentration,
agitation, anxiety, depression, and difficulty controlling
themselves2,3.
Depression
was one of the most common and specific symptoms of
menopause4-6, which may cause some serious problems
such as disability and death7,8,
leading
to significant individual, family, and society
burdens9.
Estrogen is the most used to treat depression and for relieving other
symptoms among postmenopausal women in clinical10,11.
However, several side effects and risks have been reported after
estrogen treatment, including stroke, thromboembolism events, breast
cancer, and vascular
diseases12.
Furthermore, Morrison et al . reported that hormone replacement
therapy (HRT) does not treat post-menopause including relieving
depressive symptoms in
them13.
Nowadays, women are preferring to choose treatments with herbal medicine
rather than exposing themselves to the risks associated with
HRT3,14. Researchers have proposed that
phytoestrogens, which are compounds extracted from
plants15 can be used as an alternative approach to
treating post-menopausal depression, without the risks associated with
taking
estrogens16.
There are two main types of phytoestrogens:
isoflavones
and lignans. Isoflavones are found mainly in beans, fruits, and
vegetables, especially soybeans;
Lignans are found in lentils,
cereals, wheat, and black rice, as well as fennel, sunflower seeds, and
onions17.
The efficacy of phytoestrogens remains controversial. Some research
findings have indicated a significant improvement in relieving
depression
among
post-menopausal18,19, while other studies have argued
that the treatment of soy isoflavones does not reduce
depression20.
There
has been a meta-analysis published in 2018, which included 3 studies and
316 participants (149 in the phytoestrogen group and 167 in the placebo
group) that showed phytoestrogen consumption is associated with a
significant reduction in depressive symptoms among postmenopausal
women21. However, as only three articles included all
published in 2009 and 2010, more than twice as many eligible studies
ranging from 2002 to 2017 were ignored. There are no convincing
conclusions regarding the effects of phytoestrogens on postmenopausal
depression until now.
The present systematic review and
meta-analysis of randomized controlled trials (RCTs) aim to investigate
the efficacy and safety, as well as the influencing factor of
phytoestrogens in alleviating depression among postmenopausal women.
2.Method
The protocol for this systematic review has been registered on the
International prospective register of systematic reviews (PROSPERO No.
CRD4201804493). The Cochrane Handbook for Systematic Reviews of
Interventions and PRISMA Statement helped guide the conduct and
reporting of this review22.