Why Do Antidepressants Take 6 Weeks to Work?

Until fairly recently, psychiatrists and neuropharmacologists have been puzzled by the several-week delay in onset of antidepressant efficacy of commonly prescribed mood elevators. It shouldn't take that long to boost neurotransmitter levels. But straight from central casting, the neural stem cell made its appearance in the science annals, and it was found that some antidepressants stimulate the differentiation of neural stem cells to mature nerve cells. Voila! New neurons--a feat once thought impossible!--from neural stem cells, with a little help from pharmacology. Recent work from the University of Texas supports that hypothesis.

...Antidepressants act very quickly to increase levels of natural compounds, called neurotransmitters, which nerve cells use to communicate. It takes several weeks to several months, however, for the patients who respond to such treatments to feel less depressed. Dr. Parada said this implies that some other long-term mechanism is also at work.

...Matching the timeframe for medicated patients to feel less depressed, it takes several weeks for new nerve cells to grow, Dr. Parada said. This parallel effect, he said, may mean that antidepressants need to stimulate growth of new cells in the dentate gyrus in order to achieve their full effect. _Sciencedaily

Antidepressants stimulate the production of new nerve cells in the hippocampus, and appear to protect nerve cells from apoptosis, at least in animal studies. The time delay for the mood elevation from antidepressants appears to be caused by the time to differentiation and integration of new neurons.

All this time, psychiatrists have been engaging in regenerative neuromedicine, and did not even realise it. Now that we have a better idea of what we are doing, perhaps we can learn to do it better?