Impulsivity and epilepsy: a bidirectional mendelian randomization study

Previous studies have found that patients with epilepsy are more likely to suffer impulsivity. However, the causal relationship between impulsivity and epilepsy is unknown. In this study, we conduct a bidirectional Mendelian randomization (MR) study to explore the causal relationship between impulsivity and epilepsy with recurrent seizure.

Data of the genome-wide association studies (GWAS) on 14 impulsivity traits and epilepsy were obtained from the GWAS catalog and UK Biobank. Inverse-variance weighted (IVW) and weighted median (WM) methods were utilized for MR estimates. IVW, MR-Egger regression, and MR-pleiotropy residual sum and outlier (MR-PRESSO) methods were used to assess heterogeneity and pleiotropy.

Single-nucleotide polymorphisms (SNPs) related to the lack of perseverance were associated with a decreased risk of epilepsy with recurrent seizures according to the results of IVW (odd ratio [OR] = 0.93, 95% confident interval [CI] = 0.90-0.97, P = 0.001) and WM (OR = 0.93, 95%CI = 0.87-0.98, P = 0.007). Meanwhile, heterogeneity was not observed with a Cochran Q-derived P value of 0.819 for MR egger and a P value of 0.808 for IVW. Pleiotropy was not found according to the MR-PRESSO (P = 0.273). The other 13 impulsivity traits had no causal effect on epilepsy with recurrent seizures. Meanwhile, SNPs related with epilepsy with recurrent seizures had no causal effect on the 14 impulsivity traits.

This MR study suggests that lack of perseverance may be a protective factor against epilepsy with recurrent seizures. However, epilepsy with recurrent seizures does not affect impulsivity.