Decreased brain modularity after psilocybin therapy for depression
Carhart-Harris, R. L., Daws, R. E., Erritzoe, D., Giribaldi, B., Nutt, D. J., Roseman, L., Sexton, J. D., Timmermann, C., Wall, M.
This preprint (2021) analyzed data from an open-label (n=16) and a randomised double-blind placebo-controlled study (n=43) of psilocybin (10 -; 25mg) treatment for depression, in order to identify neural biomarkers underlying antidepressant efficacy. Psilocybin (but not escitalopram) decreased brain modularity across both trials, i.e. brain connectivity became less segregated, and this correlated with improvements in depressive symptomatology.
Abstract
Objective To assess the sub-acute impact of psilocybin on brain activity in patients with depression. Design Pre vs post-treatment resting-state functional MRI (fMRI) was recorded in two trials: 1) Open-label treatment-resistant depression (TRD) trial with baseline vs 1 day post-treatment fMRI (April-2015 to April-2016); 2) Two-arm double-blind RCT in major depressive disorder (MDD), fMRI baseline vs 3 week after psilocybin-therapy or 6 weeks of daily escitalopram (January-2019 to March-2020). Setting Study visits occurred at the NIHR Imperial Clinical Research Facility.Participants Adult male and female patients with TRD or MDD. Intervention(s) (for clinical trials) or Exposure(s) (for observational studies) Study 1: Two oral doses of psilocybin (10mg and 25mg, fixed order, 7 days apart). fMRI was recorded at baseline and one day after the 25mg dose. Study 2: either: 2 x 25mg oral psilocybin, 3 weeks apart, plus 6 weeks of daily placebo (‘psilocybin-arm’), or 2 x 1mg oral psilocybin, 3 weeks apart, plus 6 weeks of daily escitalopram [10-20mg] (‘escitalopram-arm’). fMRI was recorded at baseline and 3 weeks after the 2nd psilocybin dose, which was the final day of the 6-week daily capsule ingestion. Main Outcome(s) and Measure(s) Beck Depression Inventory and fMRI network modularity. Results Study 1: In 16 adults (mean age [SD], 42.8 [10.1] years, 4 [25%] female), psilocybin therapy was associated with markedly decreased BDI scores at 1 week (mean difference, -21; 95% CI=[-27.3, -14.7], P<.001) and 6 months (mean difference, -14.19; 95% CI=[-21.3, -7.1], P<.001). Decreased network modularity at one day post-treatment correlated with treatment response at 6 months (Pearson, 0.64; P=.01).Results Study 2: In 43 adults (42.7 [10.5] years, 14 [33%] female), antidepressant effects favoured the psilocybin-arm at 2 (mean difference, -8.76; 95% CI=[-13.6, -3.9], P=.002) and 6 weeks (mean difference, -8.78; 95% CI=[-15.6, -2.0], P=.01). Specific to the psilocybin-arm, improvements at the 6-week primary endpoint correlated with decreased network modularity (Pearson, -0.42, P=.025). Conclusions and Relevance Consistent efficacy-related functional brain changes correlating with robust and reliable antidepressant effects across two studies suggest a candidate antidepressant mechanism for psilocybin therapy: decreased brain network modularity.