1. Research method
   1. Based on intervention
      1. Pseudo-experimental (also Quasi-experimental)
         1. Cohort
      2. Observational
         1. Cohort
         2. Case/control
      3. Experimental
         1. Cohort
   2. Based on Analysis
      1. Qualitative
      2. Quantitative
   3. Based on Time
      1. Before & After
         1. Cohort
      2. Cross-sectional
         1. Cohort
         2. Case/control
         3. Cohort
      3. Longitudinal
         1. Cohort
2. Publication type
   1. Surveys
      1. Instrument validation studies
   2. Reviews
      1. From other studies (summary from others experience)
         1. Scoping review
         2. Narrative review (Umbrella)
         3. Systematic reviews
         4. Meta-analysis
         5. Network Metaanalisis
      2. From real world evidence (summary from own experience)
         1. Case report
         2. Case series
      3. Mixed
         1. Guidelines
         2. Consensus
   3. Randomized Controlled Trials
      1. Blinded
      2. Partially blinded
      3. Open label
   4. Other Statistical Model
      1. Correlations
      2. Advanced models
3. Causal inference
4. Possible association