Background: Heart rate variability (HRV) is a potential biological marker for major depressive disorder (MDD) in people with and without coronary heart disease (CHD). Depression has predominantly been examined as a categorical variable and compared to limited numbers of HRV measures. Confounders, particularly gender, methodological differences and small sample size. have previously yielded heterogeneous findings.

Objectives: This study aimed to ascertain if linear correlations exist between psychometric test scores and several HRV measures in people with and without CHD.

Methods: Multiple linear regression analysis was used to correlate HRV measures with psychometric measures of mood and anxiety as continuous variables, with covariation for age and gender, in 48 participants with CHD, 39 without CHD and the entire cohort of 87 participants. Forty-seven time domain, frequency domain and non-linear HRV measures from 24-hour cardiac recordings were examined.

Findings: Mood is correlated with longer term HRV measures, with covariation of age and gender in the entire study cohort. In the CHD cohort, mood is correlated with short and longer term HRV measures with covariation of age. In the non-CHD cohort mood is correlated with longer term HRV measures only, which is not consistent with some findings in the literature.

Conclusions: This study is small and gender is unevenly distributed across CHD and non-CHD cohorts. The results obtained for the non-CHD cohort may be confounded by gender. People with CHD are also likely to be in a different stable state of autonomic control from people without CHD, which may also explain differences in the results.