Well, Wyeth is still on the chemical imbalance train with their knockoff of their current bestselling antidepressant Effexor, which may be gracing your pharmacy before long. The new drug is called Pristiq and Wyeth is offering up the following as part of its early PR campaign for the drug:
In the area of depression, Pristiq is expected to improve the balance of serotonin and norepinephrine as compared with serotonin reuptake inhibitors (SSRI) because of its pharmacologic profile as a dual reuptake inhibitor.Well, whoopee! Will it work any better than antidepressants that attempt to target either norepinephrine or serotonin? Nope. Why? Because a reliable imbalance of either neurotransmitter has never been found in depression. That's right -- never. But Wyeth continues to run with the chemical imbalance program because a lot of people have been indoctrinated, through advertising or perhaps through teachers who themselves lacked much education on the topic, to buy into this whole chemical imbalance deal.
I'm not saying that biology does not impact depression. I am saying that our current level of understanding in this area is much more speculation than it is fact. I do not believe there is a single serious scientist who would stick his/her name behind the simple "chemical imbalance" theory of depression.
And the name Pristiq? It would appear that Wyeth is aiming for a close resemblance to "Pristine," which is a bit ironic given the side effect profile of Pristiq (which will likely resemble that of Effexor closely).
More on Pristiq in an interesting post at Depression Introspection.