"Ketamine's got two actions": a direct antidepressant effect on different neurotransmitters than tablet antidepressants target — working "within sort of 48 hours" for most people — and, the part Lauren calls "really really sexy," it "stimulates the growth of new pathways in the brain."
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The first action explains why ketamine works when tablets fail: "the neurotransmitters that ketamine targets are different to the ones that are targeted by tablet antidepressants — so that's why when people sort of fail tablet antidepressants, ketamine will still work for them." It's also fast: tablets "take a really long time to work," while "ketamine will work for most people within sort of 48 hours of treatment."
The second action is the neuroplasticity. Thought patterns "over a period of time are becoming grained in our brain networks," which is why changing a habit is "bloody hard to do as an individual" — "and then you get ketamine and you get this burst of fertility for growing new pathways." Combined with behavioural activation or psychotherapy, "suddenly your therapy actually works for you" — the kind of change "that is actually really difficult to generate in a brain that's had chronic pathways for a really long time."