To the Editor: Amanda J. Law, Ph.D., et al. (1) reported decreased mRNA for spinophilin in the hippocampal formation in patients with schizophrenia and mood disorders. The potential implications of this abnormality are curious since spinophilin is involved in limiting or decreasing the length of dendritic spines. Spinophilin immunoreactivity is predominantly (although not exclusively) localized to dendritic spines (2), for which it is a meaningful marker, with hippocampal spine density and spinophilin immunoreactivity both increasing in response to estrogen (3). However, spinophilin is not necessary for the formation of spines, which are increased in density in young spinophilin knockout mice or for their removal, since spine density returns to normal when such animals mature (4).