[Sleep spindles in post traumatic stress disorder: significant importance of selective serotonin reuptake inhibitors]

Sleep spindles (SS) are conducted by the thalamus during sleep and have an inhibitory effect on information rising through the thalamus to the cortex, probably representing the mechanism called Arousal Inhibitory Mechanism. They appear during sleep stage 2 but also in stages 3, 4 and REM (Rapid Eye Movements). Patients with post traumatic stress disorder (PTSD) complain of insomnia, although objective studies have revealed that their sleep is deeper and their awakening threshold is higher. The relationships between PTSD or selective serotonin reuptake inhibitors (SSRI) to SS density are not described in the literature.

This study aimed to examine the hypothesis that the higher awakening threshold reflects an active defense process which would be manifested in increased sleep spindles in patients with PTSD.

A total of 15 PTSD patients (36.3 +/- 11.4 years) comprised the research group and 15 healthy students (27.3 +/- 2.18 years) comprised the control group. Participants underwent a polysomnography study in the sleep laboratory at 'Rambam' Hospital, Haifa, Israel.

There was no difference in the sleep spindles density per minute during stage 2 between the research group (2.54 +/- 1.14) and the control group (2.86 +/- 1.3). However, sleep spindles density was highly affected by selective serotonin reuptake inhibitors, such that PTSD patients treated with SSRI's had significantly higher spindles density than the remaining PTSD patients (3.25 +/- 1.1 vs 1.72 +/- 0.46, p=0.0044). Stage 2 was shorter in the research group (47% +/- 8.75%) compared to the control group (58% +/- 8.5%, p=0.0014), while stages 3, 4 were longer (32% +/- 8% vs 18% +/- 6.26%, p<0.001).

Sleep spindle density was generally not increased in patients with PTSD, thus other mechanisms are probably responsible for their stabilization of sleep. SSRI's were found to have an important role in spindles density, which supports a serotonergic mechanism in the stabilization of sleep, although it requires further research.