Higher plasma leptin and lower C-peptide levels are associated with depression: A cross-sectional study

Depression is a seriously disabling public health problem with very high world-wide prevalence. This study examined cross-sectional association between depression and both inflammatory markers and laboratory data involved in metabolic disturbance among Japanese subjects.

This cross-sectional study is a secondly analysis for the data of the Iwaki Health Promotion Project 2014 (1167 subjects). Plasma inflammatory markers and laboratory metabolic data involved were used. Center for Epidemiologic Studies Depression Scale (CES-D) was used to assess the prevalence and severity of depressive symptoms. Participants with CES-D scores ≥ 16 were assigned to the 'Depression' group (Group D). Differences between group Non-depression (ND) and D were estimated using χ² test or Fisher's exact test for categorical variables and Student's t-test or Mann-Whitney test for continuous variables. Multivariate logistic regression analysis was also used to identify characteristics, co-morbidities, conditions and laboratory data associated with depression after adjusting for possible confounding factors.

There were significant differences in sex, age, blood pressure, interleukin (IL)-6, fasting blood sugar (FBS), hemoglobin A1c (HbA1c), and cortisol level using univariate analysis between the two groups. However, multivariate logistic regression analysis indicated that lower age, lower C-peptide, and higher leptin were associated with the depression.

This study showed that higher plasma leptin and lower C-peptide levels were significantly associated with depressive symptoms. No significant association was found between plasma inflammatory markers and depressive symptoms after adjusting for possible confounding factors.