Over the past decades research into psychotherapy has disproportionately focused on treatment outcomes while largely neglecting the underlying processes. Consequently, the understanding of how, for whom, and under what conditions psychotherapies are effective remains limited. Our aim was to identify, define, and classify the individual, treatment-specific elements embedded in psychological and social interventions delivered by non-specialist providers (NSPs) for people with common mental disorders such as depression and anxiety.

We developed a taxonomy by systematically reviewing 11 evidence-based intervention manuals and coding their treatment-specific elements. The resulting three-tiered taxonomy comprises 39 techniques, organized into nine components, and further grouped into five overarching families. Each element was assigned an intensity score to distinguish between core and peripheral elements.

All manuals (100%) included “psychoeducation” and some form of “cognitive reframing”, particularly strategies that assist clients in linking thoughts, emotions, and behaviors. “Problem management” and “relaxation” were also widely represented, as were techniques to “strengthen social support” (73%). “Interpersonal focus” (64%) and “behavioral activation” (45%) were moderately present, while “acceptance and mindfulness” and “emotion regulation” appeared less frequently (27%).

Taxonomies, particularly those based on transdiagnostic frameworks, help move beyond one-size-fits-all approaches in psychotherapy research and practice. Taxonomies are foundational to predicting how individuals with specific characteristics will respond to the active elements embedded within therapy protocols.