The Regression Discontinuity Design (RDD) is an econometric quasi-experimental design aimed at estimating the causal effects of a treatment by exploiting naturally occurring treatment rules. This design can be applied in any context where a particular treatment is administered according to a pre-specified rule (guideline) linked to a continuous variable. Such thresholds often exist in primary care in the context of drug prescription. Examples include the prescription of anti-hypertensive drugs when blood pressure exceeds 140/90 mmHg and prescription of selective serotonin uptake inhibitors (SSRIs) for patients exhibiting more than 4 symptoms in the ICD-10 classification of depression.