By performing cross-tissue and multiple-gene conditioned transcriptome-wide association studies (TWAS) for 23 tissues of the GBA for three clinically related inflammatory diseases of the gastrointestinal tract (CD, UC, and PSC) and four diseases of the mind and brain (SCZ, MDD, BD, and ADHD) we identified susceptibility genes NR5A2, SATB2, and PPP3CA shared between IBD (CD/UC) and SCZ that are (genetically) expressed both in intestinal and brain tissues. Here, PPP3CA is linked to attention deficit-hyperactivity disorder.