Psychedelic Assisted Therapy as a Complex Intervention: Implications for clinical trial design

The rapid growth of psychedelic-assisted therapy (PAT) research and considerable debate around PAT’s promise and limitations as a healthcare intervention demand addressing theoretical gaps in PAT development. Traditional clinical trials evaluate PAT as a simple pharmaceutical treatment, overlooking its inherent complexity as a multi-component intervention. This position piece advocates for applying the UK Medical Research Council’s complex intervention framework to PAT, emphasising: theory of therapeutic change, structured development phases, contextual interactions, and stakeholder inclusion. The limitations of standard explanatory clinical trials, particularly their challenges with real-world validity, are contrasted with pragmatic clinical trial designs. Pragmatic randomised controlled trials (RCTs), informed by the PRECIS-2 tool, provide a pathway to align PAT clinical trial designs with real-world applications. This approach enables the exploration of how PAT interacts with existing healthcare systems potentially optimising its therapeutic utility in the intended patient population. Furthermore, we discuss the philosophical divergence between perspectives on PAT’s efficacy, contrasting drug-centric views with psychotherapy-augmented theories and how this should influence PAT trial design. We propose the integration of qualitative data, adaptive designs, and comparative effectiveness research to refine PAT interventions and address the shortcomings of conventional double-blind RCTs. By leveraging academic and community-led research, this work proposes a pluralistic evidentiary model, enabling more inclusive, practical trial designs that might be considered in expanded evidence assessments. This approach holds the promise of advancing psychedelic medicine while avoiding the historical pitfalls that limited its development in prior decades.