Good morning or good evening: Daytime and cortisol as modulators of exposure therapy outcomes.
Gianna Zorzini, Patricia Ritter, Gianandrea Pallich et al.
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In 30 seconds
This double-blind randomized controlled trial examined whether treatment time and endogenous cortisol were associated with outcomes of group exposure therapy in 53 participants with spider-phobia symptoms. Participants began a four-hour therapy session at either 8 a.m. or 5 p.m.; symptoms and behavioral avoidance were assessed before treatment, one week later, and at three-month follow-up. Fear and avoidance improved significantly after therapy, but symptom improvement did not differ between morning and evening groups (all p > 0.05). Exploratory analyses linked a lower cortisol change during individual exposure with greater reductions in phobic fear.
Key findings
- Phobic fear improved after exposure therapy (FSQ: η²ₚ=0.70; SPQ: η²ₚ=0.59), as did avoidance behavior (η²ₚ=0.70).
- Morning participants had higher cortisol levels than evening participants (p = 0.036), but symptom improvement did not differ between groups (all p > 0.05).
- Lower cortisol change (AUCi) during individual exposure was associated with greater improvement in phobic fear (FSQ: η²ₚ=0.20; SPQ: η²ₚ=0.11).
Why it matters
The findings suggest that scheduling exposure therapy in the morning rather than the evening did not improve outcomes in this sample, despite higher morning cortisol. The exploratory association between cortisol change and fear reduction raises a possible biological correlate of response, but does not establish that cortisol change causes improvement or can guide treatment decisions.
What to keep in mind
The cortisol-change findings were exploratory, and the study involved participants with spider-phobia symptoms receiving a specific group-based, four-hour intervention, limiting generalisation to other anxiety disorders or therapy formats.