This is indeed the best theory we have at this time. Note, however, that this is a empirical theory. The correlation between suicidal risk and antidepressants that are more activating compared to those that are less activating is weak, at best, in comparative risk studies. There is no doubt a neurophysiological explanation for why this class of psychoactive pharmaceuticals increases suicidal risk at the beginning of therapy. However, the current neurological underpinnings of suicidality are very poorly understood, and the influences on it even less so. As such, we are left with the above. One just needs to remember it is a very broad explanation for an extremely poorly understood phenomenon.