Lorazepam and the sleep EEG ́s microstructure: A novel approach to quantitative pharmaco-EEG investigations

Background: When searching for reliable and specific markers for certain psychiatric diseases, preliminary investigations of the sleep EEG’s microstructure point to the view that the delta/beta correlation coefficients during NREM sleep appear increased in depressives, but not in schizophrenics. Therefore, this parameter could be hypothesized to be a marker of depression. On the other hand, subchronically, paroxetine medication in healthy subjects produces the opposite finding: a decrease in the delta/beta correlation coefficients during NREM sleep, which might be interpreted as evidence of the antidepressant action of the drug. Of course, a close connection between this effect and the antidepressant efficacy of this drug has not been demonstrated to date. Objective: The aim of the present paper was to illuminate the sleep EEG’s microstructure under the influence of the benzodiazepine lorazepam. This drug influences the conventional sleep EEG parameters very similarly to most of the antidepressants. However, it should be assumed that benzodiazepines do not act as antidepressants. Therefore, the question arises as to whether lorazepam alters the delta/beta correlation of the sleep EEG in the same way as paroxetine. Method: Separately for REM and NREM sleep we calculated the correlation coefficients between different frequency bands (delta, theta, alpha, beta) from sleep EEG data of healthy subjects (n=8) from Pz-Cz through the night in a double-blind placebo-controlled cross-over design (single dose of 2.5 mg lorazepam). Results: Despite the alterations of the conventional sleep EEG parameters, no influence of lorazepam on the sleep EEG’s microstructure could be observed. Conclusions: Assuming the findings of the present paper can be replicated in a larger sample size, NREM alterations of the sleep EEG’s delta/beta oscillations may be characteristic for depression and antidepressants (German J Psychiatry 2000;3:13-18)