MAO activity and EEG sleep in primary depression

The relationship between subjective sleep estimation and objective sleep variables in depressed patients

INTRODUCTION

To our knowledge there is no evidence in the literature about the relationship between subjective sleep estimation and objective sleep variables in depression. It is not known whether the subjective estimation of sleep quality and sleep duration is directly related to any objective sleep variable in depressed patients.

METHODS

Thirty patients with major depression and 10 healthy subjects have been investigated in our sleep laboratory during 1 or 2 consecutive nights after 1 night for adaptation. Every subject, after final awakening in the laboratory, answered questions concerning the subjective feelings about sleep duration, number of awakenings and sleep depth. We compared the sleep estimation in both groups and calculated the correlation between objective and subjective sleep variables in depressed patients.

RESULTS

The degree of a wrong sleep estimation in depressed patients is larger than in healthy subjects. Slow wave sleep (SWS) in depressed patients correlates positively with the subjective estimation of sleep duration. Eye movement density in REM sleep correlates with the subjective estimation of the number of awakenings.

CONCLUSION

SWS in depression has a positive influence on the subjective feeling of sleep duration while phasic REM sleep activity has a negative influence.

Sleep disturbance in depression reconsidered

The well documented observation of a characteristic sleep disturbance in depression has been accorded a good deal of significance. Several current hypotheses regarding the etiology of depression, are based on these findings. However, a review of the descriptive studies shows that care has not generally been taken either to restrict or objectively measure daytime sleep. Evidence is presented suggesting that daytime sleep may occur in depressed patients more frequently than commonly thought and that, in normal subjects, daytime napping can result in nocturnal sleep changes similar to those seen in depressed patients. A model is proposed in which the nocturnal sleep disturbance in depression reflects the occurrence, during the daytime, of frank slow wave sleep or periods of large amplitude, slow wave EEG activity as a consequence of a dampening of the circadian rhythm of sleep propensity.

REM sleep and depression: further use of computer simulation to test the phase-advance hypothesis

A phase advance of the circadian rhythm of rapid eye movement (REM) sleep propensity relative to the sleep-wake cycle has been proposed to account for the abnormalities of REM sleep commonly found in depressed patients. One implication of this hypothesis is that a phase delay of sleep in normal subjects should produce the same abnormalities of REM sleep. The hypothesis was tested by computer simulation using equations based on data derived from normal subjects who had experienced phase shifts of their bedtime. At phase delays of between 4 and 6 hours (an estimate of the putative phase advance in depressed patients), the mean REM latency and the mean duration of the first REM period predicted by the equations did not differ significantly from those observed in depressed patients. The findings with respect to the distribution of REM latency were more equivocal.

Early morning awakening in unipolar depressives with higher levels of platelet MAO activity

Platelet monoamine oxidase (MAO) activity was analyzed in 51 patients with Major Depressive Disorder. The enzyme activity was correlated univariately and multivariately using split-half techniques with affective subdiagnosis, sex, body measures, and a great many depressive symptoms. The results indicate that unipolarly depressed patients with higher levels of platelet MAO activity woke up earlier in the morning than they had before becoming depressed. Waking up early appeared to be one least common denominator behind higher MAO activities and a unipolar subdiagnosis. Earlier reports on univariately significant differences in MAO activity between affective subdiagnoses or between the sexes were not replicated. Positive trend correlations were found between homovanillic acid and 5-hydroxyindoleacetic acid in cerebrospinal fluid and platelet MAO activity. Urinary free cortisol correlated significantly with platelet MAO activity, but only in unipolars.