To investigate the levels of 5-hydroxytryptamine receptor 1A (5-HTR1A) promoter methylation in peripheral blood of patients with bipolar disorder during their depressive episode, and to explore the relationship between the methylation levels and depressive symptoms of the patients.

Blood samples were collected from 65 patients (study group) with bipolar disorder who were in the stage of depressive episode and 59 healthy people (control group) from August 2017 to August 2018 at Mental Health Center of Guangdong, the Third People's Hospital and Jiangmen City People's Hospital. Methylation levels in the 5-HTR1A promoter region in peripheral blood cells were detected and compared by pyrosequencing. In the study group, the Hamilton depression scale score was used to assess the patients′ depressive level and correlation analysis was conducted between methylation levels and the Hamilton depression scale scores.

The methylation level of 5-HTR1A promoter region in peripheral blood was significantly reduced in the study group than in the control group [(46.86±6.75)% vs (50.03±8.85)%, t=2.255, P=0.013] . A negative correlation was found between Hamilton depression scale scores and methylation levels in the study group (r=-0.631, P<0.01).

There is a correlation between depressive episode and the methylation levels of 5-HTR1A promoter region in peripheral blood of patients with bipolar disorder.