ELI5: Recently I heard that a new theory about how antidepressants work is that instead of fixing a "chemical inbalence", they actually drastically improve/increase neuroplasticity. How would better neuroplasticity make you less depressed and/or anxious?

ELI5: Recently I heard that a new theory about how antidepressants work is that instead of fixing a "chemical inbalence", they actually drastically improve/increase neuroplasticity. How would better neuroplasticity make you less depressed and/or anxious?