It is common for a doctor to promise five good years by going on L-dopa or such but to also admit that the patient could die five years sooner than would happen without any treatment at all. This is not delaying the advance of the disease. It is advancing the disease but with a period of time where relief of symptoms can be offered in exchange. Carlsson's group developed the first SSRI that led to the new depression drugs such as Prozac. Kandel's work was very useful but he makes a mistake if assuming that the serotinergic regions of the brain are responsible for memory.
Memory occurs in the entire brain.
Memory, short or long-term, does not only take place in cells that use serotonin. Again, understanding these processes could help doctors one day unravel the reason why memory is lost in conditions such as Alzheimer's, and could even produce memory-enhancing drugs. The genes have an effect on the way the body works, but there are processes inherent in the nature of the ways nerve cells relate to each other that are the reason for conversions from short to long-term memory. The genetics movements in medicine are getting a bit grandiose in the claims of how much they will be able to accomplish following that route. It is wishful thinking of these companies that they could market yet another drug that would cause dependence, create withdrawal when suspended, and require you to spend large amounts of money to get the promised results.