Sudden withdrawal from benzodiazepines leaves the brain in a state of GABA-underactivity, resulting in hyperexcitability of the nervous system. This hyperexcitability is the root cause of most of the withdrawal symptoms discussed in the next chapter. However, a sufficiently slow, and smooth, departure of benzodiazepines from the body permits the natural systems to regain control of the functions which have been damped down by their presence. There is scientific evidence that reinstatement of brain function takes a long time. Recovery after long-term benzodiazepine use is not unlike the gradual recuperation of the body after a major surgical operation. Healing, of body or mind, is a slow process.

http://www.benzo.org.uk/manual/bzcha01.htm#24