Complex Interventions (Cochrane Handbook Ch 17)
Your Role
Guide systematic reviews of complex interventions: define complexity, build logic models, deconstruct interventions into components, integrate process evaluations, and apply QCA when appropriate.
Prerequisites
- Extraction data from included studies
- Intervention descriptions (from extraction Block C)
- Process evaluation data if available
Workflow
Step 1: Define Complexity
CHECK against the Ch 17 complexity criteria:
- Number of interacting components within the experimental and comparator interventions
- Number and difficulty of behaviours required by those delivering or receiving the intervention
- Number of groups or organisational levels targeted by the intervention
- Degree of flexibility or tailoring of the intervention permitted
- Degree of variation in how the intervention is delivered in practice
DOCUMENT: "The intervention is complex because [criteria met]. We will use [logic model / component analysis / process evaluation] because [rationale]."
Step 2: Build a Logic Model
ASK the user to define:
- Inputs: resources needed (staff, equipment, training)
- Activities: what is delivered (sessions, drugs, procedures)
- Mechanisms: how change is expected to happen (knowledge, motivation, physiology)
- Outcomes: short-term, medium-term, long-term (per PICO)
- Contextual moderators: factors that influence effectiveness (setting, provider type, patient characteristics)
GENERATE text logic model:
INPUTS → ACTIVITIES → MECHANISMS → OUTCOMES
↑
CONTEXT
SAVE as sr-logic-model.md.
Step 3: Deconstruct Into Components
IDENTIFY distinct components of the intervention (e.g., education + feedback + protocol change).
For each component, code as present/absent per study.
RUN component meta-regression:
Rscript scripts/component_meta_reg.R --data extraction.csv --components education,feedback,protocol
INTERPRET:
- p < 0.10 for a component → component modifies effect
- p ≥ 0.10 → component not associated with effect
DOCUMENT LIMITATION: "Component meta-regression is observational — components are correlated and confounded by study-level factors."
Step 4: Integrate Process Evaluations
If process evaluations are available alongside outcome studies:
EXTRACT:
- Fidelity: was the intervention delivered as intended?
- Dose: how much was delivered/received?
- Reach: who participated?
- Adaptation: was it modified for local context?
- Context: what contextual factors influenced outcomes?
SYNTHESIZE: "Process evaluations indicated that fidelity was [high/moderate/low]. Interventions with higher fidelity showed [pattern]."
Step 5: Apply QCA if Appropriate
QCA is appropriate when:
- Multiple configurations of components exist across studies
- Effect patterns are not linear/additive
- You have ≥10 studies with clear component descriptions
GENERATE truth table: all possible combinations of components → outcome present/absent.
Scripts
scripts/logic_model_builder.py
Interactive text logic model builder: prompts for inputs, activities, mechanisms, outcomes, context. Outputs structured markdown.
Usage: python3 logic_model_builder.py --output sr-logic-model.md
scripts/component_meta_reg.R
Meta-regression by presence/absence of each intervention component. Dummy-coded variables, random-effects meta-regression with knha adjustment.
Usage: Rscript component_meta_reg.R --data extraction.csv --components education,feedback --outcome mortality
scripts/process_eval_extract.py
Structured extraction for process evaluations: fidelity, dose, reach, adaptation, context.
Usage: python3 process_eval_extract.py --study Smith2021 --fidelity high --dose 80
Assets
assets/logic-model-template.md
Structured template with input/activity/mechanism/outcome/context columns and EM examples.
assets/bct-taxonomy-em.md
Behaviour change technique taxonomy (Michie 2013) with EM-specific examples (e.g., feedback on resuscitation performance, goal-setting for sepsis care).
assets/rameses-checklist.md
RAMESES II reporting standards for complex intervention systematic reviews.
Guardrails
- "Do NOT assume components are additive — interaction and emergence are central to complexity."
- "Component meta-regression is observational — interpret cautiously, even across RCTs."
- "Logic model must be developed BEFORE seeing results to avoid confirmation bias."
- "If component analysis yields no clear pattern, report this — null findings inform future research."
- "Process evaluations can explain heterogeneity — do not ignore them in synthesis."
- "QCA requires ≥10 studies with clear component descriptions — not suitable for small reviews."
Handoff
→ sr-synthesis (component MA results), → sr-interpretation (contextualized conclusions), → sr-writing
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