Limitations
The limitations associated with the methods employed in this study are inherent to postmortem studies involving proxy-based interviews. However, the validity of such procedures, particularly with regard to the use of observable behaviors, has been well demonstrated (32), and our comparisons of data obtained using two different informants on the same subject, as well as comparisons between the comparison subject and his or her informant, further support its use on behavioral measures. On the other hand, the major problem of proxy-based interviews seems to be at the level of sensitivity (34). Nevertheless, using proxy-based techniques in both groups, we controlled for this possible bias.
Another important limitation of this study is that we focused on male subjects. How generalizable are the risk factors identified in this study to female depressed patients is an issue that deserves investigation. Of particular interest will be to investigate whether or not impulsive and aggressive behaviors play a similar role in mediating suicide in depressed women as they seem to play in depressed men.