About a year ago we published a paper linking adult neurogenesis to depression. A causal sort of ‘linking’, right? I mean, we found that, when adult neurogenesis was eliminated, mice had elevated glucocorticoids in response to stress and showed depressive-like behaviours1. So doesn’t this mean that impaired adult neurogenesis could lead to depression in humans, in the real world?
Well, it could…and we did end our paper with the following:
Because the production of new granule neurons is itself strongly regulated by stress and glucocorticoids, this system forms a loop through which stress, by inhibiting adult neurogenesis, could lead to enhanced responsiveness to future stress. This type of programming could be adaptive, predisposing animals to behave in ways best suited to the severity of their particular environments. However, maladaptive progression of such a feed-forward loop could potentially lead to increased stress responsiveness and depressive behaviours that persist even in the absence of stressful events.
We had to end it somehow – I was just happy that after 3 years of work we were DONE2! But our final speculation makes it clear that, while this chapter may be done, the story is not. And this fact was rightly pointed out in a recent commentary by Lucassen et al. in Molecular Psychiatry3, where they continue the discussion and bring up some good points. Here is a loose elaboration on some of the outstanding issues they bring up. Continue reading