Moreover, another postmortem brain study has reported decreased expression not only of QUIN but also indoleamine 2,3-dioxygenase (IDO) 1/2, and tryptophan-2,3-dioxygenase (TDO) in the ventrolateral PFC of suicide victims with depression (Clark et al., 2016). The gene discussed is TDO2; the disease is depressive symptom measurement.