Objective      To investigate the correlation between comorbid anxiety and depression (CAD) and major depressive disorder (MDD) and the changes of monoamine neurotransmitters and their metabolites in serum.       Methods

      HPLC-ECD was used to determine the levels of epinephrine (E)

norepinephrine (NE)

5-hydroxytryptamine (5-HT)

3

4-dihydroxyphenylacetic acid (DOPAC)

homovanillic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA) in sera from 26 cases of CAD patients (CG group)

19 cases of MDD patients (DG group) and 23 cases of healthy adults (HG group). The concentrations

ratios and correlation coefficients of monoamine neurotransmitters and their metabolites were analyzed.       Results      The concentrations of NE and E were 1.95±1.08 and 2.55±0.96 ng/L

respectively

in the sera from the DG group

4.51±3.4 and 4.06±2.26 ng/L

respectively

in the sera from the CG group

and 4.71±1.93 and 3.89±2.44 ng/L

respectively

in the sera from the HG group

with significant differences between each two groups (

P

0.05). The concentration of 5-HIAA and HVA was 0.9±1.5 and 1.58±1.48 ng/L

respectively

in the sera from the CG group

with significant difference from those from the HG group 0.17±0.08 and 0.76±0.39 (

P

0.05). There was obvious correlation between the changes of DOPAC and NE

5-HT and 5-HIAA

HVA and 5-HIAA in the DG group. The ratios of 5-HT/5-HIAA

5-HIAA/NE

HVA/NE and DOPAC/HVA were significantly lower in the DG group than in the HG group (

P

0.05). The ratios of HVA/NE

5-HT/5-HIAA and DOPAC/ HVA in the CG group was significantly different from those in the HG group (

P

0.05). However

there was no significant difference in the ratios between the DG and CG groups (

P

0.05).       Conclusion      The serum levels of monoamine neurotransmitters and their metabolites reflect their states of equilibrium in the brain

suggesting that the changes of monoamine neurotransmitters and their metabolites can be used as important biomarkers for diagnosis of depression.