P=4.33x10−4). Our results suggest an overlap in genetic risk factors with a decrease in the odds ratio for CUD with increased number of educational years/cognitive performance (Supplementary Figure 3A-C.). The observed decreased risk of CUD with increased age at first birth (z-score=−7.41; P=1.26x10−13) is supporting the relationship with educational attainment as number of educational years is known to correlate genetically with later birth of the first child32. In order to avoid confounding in the PRS analyses of psychiatric disorders we excluded individuals among CUD cases and the control group with a diagnosis of the psychiatric disorder being analysed. PRS for ADHD (z-score=5.10; P=3.45x10−7), depressive symptoms (z-score=4.34; P=6.58x10−6) and schizophrenia (z-score=5.47; P=4.45x10−8) were all associated with an increased risk for CUD (Figure 4).
