Glycogen synthase kinase (GSK-3β) has been implicated in the pathophysiology of mood disorders and schizophrenia. To examine its role in suicide, we determined GSK-3β messenger RNA (mRNA) in human postmortem brain from suicide and normal control subjects using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) technique. We found that GSK-3β mRNA was highly abundant in almost all of the 12 brain areas we studied. We also found a significant age effect on GSK-3β and that GSK-3β mRNA level were significantly higher in prefrontal cortex (PFC) and hippocampus of teenage normal controls compared with adult normal controls and was significantly decreased in PFC of teenage suicide but not adult suicide victims compared with respective normal control subjects. The decrease observed in the mRNA levels in teenage suicide but not in adult suicide victims may represent a neurodevelopmentally associated decrease and may be important in the pathophysiology of teenage suicide. © 2008 Springer Science+Business Media, LLC.