In reply
We reported a positive association between the intron 7 A218C polymorphism of the TPH gene and bipolar affective disorder in a sample of 158 bipolar patients (103 with bipolar I and 49 with bipolar II) and 94 controls.1 However, 2 subsequent studies failed to confirm this finding. Kirov et al2 show no preferential A218C allele transmission in a sample of 118 parent-offspring trios and McQuillin et al3 failed to replicate the initial finding in a case-control association study.