SLEEP 2022 Data Show Reduced Slow Wave Activity in Depressed Adolescents

Chiara Fontanellaz-Castiglione

In a late-breaking abstract published today during the Associated Professional Sleep Societies (SLEEP) 2022 Annual Meeting data showed the reduction of slow wave activity (SWA) in unmedicated adolescents with depression was topographically more widespread and effect sizes were larger compared with previous studies.

Electroencephalographic slow-wave activity (EEG SWA) is described as an electrophysiological signature of slow (0.5 to 4.0 Hz), synchronized, oscillatory neocortical activity. This activity is maximally expressed during non-rapid-eye-movement (non-REM) sleep, and intensifies as a function of prior wake duration in healthy individuals.

A frequent and primary complaint for individuals with major depressive disorder (MDD) is disrupted sleep. Findings from prior studies were deemed inconclusive due to samples with broad age ranges, differing medication status and variable severity of depression.

However, studies that examined adolescents with MDD discovered changes in slow wave activity. A team of investigators led by Chiara Fontanellaz-Castiglione, University Hospital of Child and Adolescent Psychiatry and Psychotherapy, University of Bern, further examined the phenomenon in the adolescent population.

Slow Wave Activity in Adolescents with MDD

Investigators enrolled 65 unmedicated adolescents between the ages of 14-17 to participate in the research. After adolescents were screened for major depressive disorder based on on a clinical interview, 35 were diagnosed.

The study objective aimed to examine sleep neurophysiology in an unmedicated sample of adolescents with and without MDD using high-density sleep electroencephalogram (EEG). In their own homes, the participating adolescents adhered to a sleep-wake schedule for 3 days before the sleep EEG night.

High-density sleep EEG, of 58 EEG derivations, was recorded. An ANOVA including age, sex and group was used to determine statistical differences between groups and slow wave acitivity was calcualted as power in the 0.6-4.6 Hz range.

Depression and Slow Wave Sleep

The reduction of slow wave activity in adolescents with major depressive disorder was significant when compared with healthy controls. Statistically significant differences were distributed over widespread brain regions with 33 derivations, according to investigators.

This demonstrated a wider range topographically, compared to former findings looking at adolescents with MDD. Results showed the effect sizes were larger as well, with eta-squared values for significant electrodes ranging between 0.11-0.28.

"This might be explained by the recruitment of an unmedicated sample, the narrow age range and the moderate to severe depression, which may help reduce variability and increases statistical power," investigators wrote.

"Our results add to the existing literature showing a reduction of SWA in depression and further our understanding of the role of sleep in adolescent depression," they concluded.