Effects of psilocybin versus escitalopram on rumination and thought suppression in depression

Introduction

Major depressive disorder (MDD) commonly involves maladaptive coping strategies such as rumination and thought suppression, which are linked to maintenance, recurrence and greater severity of depressive episodes. Thought suppression denotes effortful attempts to avoid distressing thoughts, which often backfire and increase intrusive thinking, while rumination denotes repetitive, self-focused negative thinking. Earlier research indicates both strategies are associated with poorer problem-solving and emotional processing. Selective serotonin reuptake inhibitors (SSRIs) such as escitalopram are a first-line pharmacological treatment for MDD but have only partial response rates (around 50-60%) and can cause side-effects including emotional blunting. Classic serotonergic psychedelics, notably psilocybin, combined with psychological support, have been proposed to relax entrenched cognitive habits and increase psychological flexibility, and prior qualitative and non-randomised data have suggested reductions in self-rumination after psychedelic therapy. However, no randomised trial had directly compared psilocybin with an established SSRI on standardised clinical measures of rumination and thought suppression while attempting to maintain blinding and providing an active comparator. Barba and colleagues report exploratory analyses from a previously conducted randomised clinical trial (N = 59) that compared psilocybin therapy (COMP360) with 6 weeks of escitalopram for MDD. The present paper focuses specifically on the 22-item Ruminative Response Scale (RRS) and the White Bear Suppression Inventory (WBSI) as outcomes. The primary hypothesis was that psilocybin therapy would produce greater reductions in RRS and WBSI at the 6-week primary end-point than escitalopram. Secondary hypotheses examined whether reductions were driven by participants meeting conventional treatment-response criteria (≥50% reduction on QIDS-SR-16) and whether acute subjective experiences or subsequent psychological insight following psilocybin sessions related to changes in rumination and suppression.