Neurogenesis is the development and growth of new neurons in the brain. For most parts of the brain, this mainly occurs before you are born, when the brain in first developing. However, some parts of the brain, including the hippocampus (responsible for memory functions and spatial orientation among other things), continue small amounts of neurogenesis in adulthood. Research on depression has suggested that a lack of neurogenesis may play a role in this mental disorder, especially because antidepressant medication seems to stimulate neurogenesis in the hippocampus. A recent study published in Translational Psychiatry claims that this type of neurogenesis appears to be necessary for long-term recovery from depression.
The problem with a lot of the research mentioned above is that it was done with rats. Animal models are a good place to start, but are we really ready to claim that hippocampal neurogenesis is a part of sustained remission from a complicated and fairly human mental disorder like clinical depression? Are we so sure that their paradigm of depression in rats replicates depression in humans? I think that animal models can contribute a lot to this field but I also think we should be very careful about generalising results to humans before any research with human samples have been done. For example, the article mentioned above in Translational Psychiatry did not even mention that the sample comprised of rats in the abstract.