The relationship between psychiatric illness and the circadian pattern of heart rate.

Objective: The aim of this study was to investigate the relationship between psychiatric status and the circadian pattern of heart rate.Method: Serial 24-hour recordings of minute average heart rate were obtained from 30 normal volunteers and 200 patients representing a range of DSM-III-R diagnoses. Records were compared in terms of their circadian 'morphology' and grouped into different pattern types. The distribution of patterns in different diagnoses was analysed statistically.Results: It was found that states such as generalised anxiety and depression are strongly associated with a distinctive circadian pattern, whereas others such as somatoform disorder show more variation in this regard. Serial recordings show that the relationship between psychiatric status and circadian pattern is state-dependent; a change in clinical status leads to a change in the circadian pattern.Conclusions: The presented findings together suggest that there is a systematic relationship between psychiatric status and heart rate in which core physiological differences between certain states are reflected in distinctively different circadian patterns of activity. The state-dependent nature of this relationship suggests obvious practical applications, and examples are given of how these adjunct data can provide objective indices of clinical status and change. At a theoretical level, the physiological dimension revealed by these data may help to define more reliable syndromal distinctions between various clinical manifestations and hence contribute to a more robust nosology.