In mice with complete or nearly complete loss of 5-HT (Figure 1, No 5-HT; Table 1, TPH2 or TPH1/2 double knockout), 5-HT1A inhibition of both pyramidal and interneurons is predicted to be inactive and tonic interneuronal inhibition of pyramidal neurons to predominate, thereby reducing anxiety. This evidence concerns the gene HTR1A and Anxiety.