Polysomnographic Findings in Major Depression and Generalized Anxiety Disorder
Major depression and GAD show distinctly different PSG patterns: depression demonstrates shortened REM latency and increased REM density, while GAD shows prolonged REM latency with preserved REM architecture, making PSG a useful tool to differentiate these conditions.
Major Depressive Disorder PSG Findings
Sleep Continuity Disturbances
- Increased wake after sleep onset (WASO) with frequent awakenings and stage shifts throughout the night 1, 2, 3
- Prolonged sleep onset latency (>10 minutes), which predicts recurrence risk in younger patients 4
- Reduced total sleep time and decreased sleep efficiency 1, 5, 3
- These continuity disturbances are most pronounced in the first and last thirds of the night 3
REM Sleep Abnormalities
- Shortened REM latency is the hallmark finding that differentiates depression from anxiety disorders 2, 5, 4
- Increased REM density (more rapid eye movements per unit of REM time) 4
- Deficit in REM sleep duration, particularly in the first and last thirds of the night 3
- Reduced REM latency during acute episodes predicts higher relapse rates after treatment discontinuation 4
Non-REM Sleep Changes
- Reduced slow-wave sleep (SWS), especially in the first third of the night 5, 4, 3
- Decreased Stage 2 sleep duration compared to healthy controls 1
- The SWS deficit is more pronounced in adults than in children/adolescents with depression 4
Clinical Significance
- PSG abnormalities in depression can predict clinical course: delayed sleep onset (latency >10 minutes) predicts 39% probability of recurrence at 12 months versus 15% in those with normal sleep onset 4
- Linear discriminant analysis using PSG variables correctly predicts depression diagnosis in 88% of cases 5
Generalized Anxiety Disorder PSG Findings
Sleep Continuity Pattern
- Prolonged sleep onset latency is the primary finding 1
- Reduced total sleep time compared to healthy controls 1
- Decreased Stage 2 sleep duration 1
- Fewer awakenings and stage shifts compared to major depression, particularly on the first night and across multiple nights 1, 2
REM Sleep Characteristics
- Prolonged REM latency (mean across multiple nights), which is the key differentiating feature from depression 1, 2
- Shorter REM duration on the first night of recording 1
- Preserved REM architecture without the increased REM density seen in depression 2
Distinguishing GAD from Depression
- GAD patients show significantly longer REM latency than depressed patients, even when GAD presents with significant depressive symptoms 2
- GAD demonstrates fewer stage shifts and awakenings compared to major depression 2
- These differences remain consistent even in GAD patients with comorbid significant depression 2
Key Differentiating Features
The most reliable PSG marker to distinguish major depression from GAD is REM latency: shortened in depression, prolonged in GAD 1, 2. This finding holds even when anxiety and depression co-occur 2.
Common Pitfalls to Avoid
- Do not assume all psychiatric patients show shortened REM latency—this is specific to depression, not anxiety disorders 1, 2
- First-night effects can confound results; multiple-night recordings provide more reliable data, particularly for REM latency measurements 1, 2
- Children and adolescents with depression show less pronounced PSG abnormalities than adults, so adult findings cannot be directly generalized to younger populations 4
Clinical Utility
- PSG can serve as an objective biomarker to differentiate anxiety from depressive disorders when clinical presentation is ambiguous 1, 2, 5
- Sleep continuity disturbances and delayed sleep onset in depression predict recurrence risk and should inform treatment intensity 4
- Major depression with objective insomnia shows a similar PSG pattern to primary insomnia (excess WASO, SWS/REM deficits, non-shortened REM latency), suggesting shared hyperarousal pathophysiology 3