With the increase of social pressure and the pace of life, mental illnesses, such as anxiety disorder, or even depression disorder, are increasingly common in perimenopause women due to hormonal metabolic disorders (1). Patients with perimenopausal syndrome present a series of symptoms, such as dysphoria, irascibility, mood swings and uncontrolled rage, which have a negative impact on the patients themselves and their families and lead to a lower quality of life (2,3). The main reasons for these symptoms are the decline of ovarian function and significant reduction of endogenous estrogen secretion.

Previous research has shown that the level of brain-derived neurotrophic factor (BDNF) in peripheral serum is closely related to the severity of depression (4), as it is an important component in neurotrophic factors. BDNF in the cells of brain tissue is composed of the tissues such as neurogliocyte and neuron in the brain tissue cells (5) and BDNF in peripheral serum is composed and secreted by blood platelets. When the composition or content of blood palates is stimulated by external or internal factors, a reduction or increase is observed in the synthesis and secretion of BDNF (6). When patients have depressive symptoms, a significant reduction in the content, synthesis and release of BDNF in peripheral serum is observed (7). As the inflammatory system is regulated and mediated by multiple inflammatory factors, antidepressants are often used in the treatment of the majority pf patients with depression disorder to lower the level of inflammatory factors and obtain a better treatment effect (8). However, more research data are necessary to support the related mechanisms.

Perimenopausal syndrome refers to the related clinical manifestations presented during the period from the first time of clinical manifestation of menopause to the time of the last menstruation. It is during this period that the probability of depression is increased (9). Therefore, the investigation on the risk factors associated with depression in perimenopausal syndrome patients can avoid or reduce the onset as much as possible or achieve the goal of early detection and early treatment.

As patients with depression are often in the psychological state of low mood, it is easy to cause substantial organ dysfunction, if not treated seriously for a long time. Depression is a common impaired mental function syndrome (10), especially in this rapid development world, the incidence of depression has become higher and higher with the increase of life pressure (11). Patients with perimenopausal syndrome, due to the metabolic disorders of hormone levels, are more likely to develop autonomic nerve dysfunction (12), which can be further developed into depression. Some patients have the symptom of depression from the beginning of perimenopause which may continue or repeat until menopause, while it may even continue for 5–10 years after menopause to overcome by patients (13), which will bring serious negative effects on patients themselves and their families as well as society. The most essential reason of having depression for patients with perimenopausal syndrome is the rapid reduction of endogenic estrogen content, resulting in moodiness, mainly manifested as irritability and depression (14). Thus, estrogen is often used in the clinical treatment of perimenopausal syndrome, which can effectively improve patients' depressed mood and promote their life quality (15). Relevant research data indicated that the use of exogenous estrogen in the treatment of perimenopausal syndrome can lower the inflammatory factor level and increase BDNF level, which can avoid onset of depression or effectively improve the severity of depression (16). However, this conclusion is necessary to be supported by more research data. BDNF is a protein component (17) with wide application existing in both central nervous system and peripheral nervous system of mammals, which can defend against anxiety and depression by mediating synapses by accelerating the differentiation of certain neurons (18). Hippocampus in the central nervous system is the main place where BDNF expression is produced. When BDNF content decreases, the patient will be found in an obvious depressive state (19). This study found that BDNF level in the group of perimenopausal syndrome patients with depression was significantly lower than that in the group without depression and BDNF was negatively correlated with SDS score, which was consistent with the conclusion.

The most common therapy for patients with depression is to use antidepressant. Research has shown that there is an obvious decline in patients' inflammatory factor level in peripheral serum during the use of antidepressant, thus inflammatory factor levels in peripheral serum are considered to be correlated with depression and its severity (20).

The conclusion from this study is that inflammatory factor levels in peripheral serum in depression group of patients with perimenopausal syndrome are significantly higher than those in non-depression group and inflammatory factor levels are positively correlated with SDS scores. In general, inflammatory factor levels in peripheral serum and BDNF level have important reference value in the depression occurred during perimenopause and can be regarded as the marker in evaluating the treatment effect of drug therapy on depression disorder. The decline of BDNF level in peripheral serum and increase of inflammatory factor levels demonstrate that the patient is more likely to develop depression disorder simultaneously or the depressive symptoms may be exacerbated. Therefore, BDNF level and inflammatory factor levels in peripheral serum have great significance in the diagnosis and treatment of perimenopausal syndrome.