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Letters to the Editor
January 1999

Tryptophan Hydroxylase Gene and Manic-Depressive Illness

Arch Gen Psychiatry. 1999;56(1):98-99. doi:10.1001/archpsyc.56.1.98

We read with interest the article on a positive association between a polymorphism in the tryptophan hydroxylase (TPH) gene and manic-depressive illness.1 The authors found a significantly increased rate of the "A" allele in patients compared with control subjects (52% vs 36%).1 The TPH gene encodes for the rate-limiting enzyme of serotonin synthesis, making it a strong candidate gene for manic-depressive disorder; therefore, we attempted to replicate these results.