However, perhaps the greatest shortcoming of In Search of Madness is its omission of a majority of recent neurobiological studies. Most of the book appears to have been written in the mid-1990s, yet the most interesting neurobiological studies have been published since that time. Among the author's 1,018 references, only 18 percent are from 1997 or after. Heinrichs includes a few references from 2000, which suggests that he had the option of including these more recent data. Given that the most recent studies are now available online, there was no reason not to include them. Furthermore, because we have been measuring verbal memory and P50 for 35 years but presynaptic glutamate for only five, the comparisons hardly seem fair.