Most writers become acquainted one time or another with the creative mental brick wall called writer's block. Basically, those wonderful times when the words end up on one side while the writer beats his head against the other. I once thought writer's block was an avoidance mechanism, sort of like fainting spells were for Victorian women, but over the years I've seen too many friends suffer through it to doubt its authenticity or tenacity.
The alleged flip side of writer's block is a condition called hypergraphia, aka the uncontrollable urge to write or produce in other media. Van Gogh apparently suffered from it, as did Dostoevsky and Stevenson (although the latter may have induced it via cocaine abuse.) Not all prolific writers are hypergraphic, but we're usually accused of it at some point or another during our careers.
A few years back, neurologist and Harvard Medical School teacher Dr. Alice W. Flaherty made some minor ripples with her book about both conditions, The Midnight Disease, which examined the creative mind as it suffers through both disorders. Although any mention of writer's block garners instant empathy from colleagues, there wasn't a lot of weeping around the industry over the plight of the hypergraphic. Like being thin and rich, apparently there is no such thing as writing too much. Unless it's someone else who's doing it, and selling it.
The late Dr. Norman Geschwind, another Harvard notable who made a name for himself in behavioral neurology, cited hypergraphia as a symptom of epilepsy; one of eighteen special personality farts created by temporal lobe complex partial seizures. He labeled those afflicted as victims of interictal personality disorder. That most prolific writers and artists do not have epilepsy was merely one of those tiny insignificant details that must have escaped his notice.
I don't agree with the diagnosis of hypergraphia as being a catch-all explanation for the prolific. Nor do I think everyone with writer's block is suffering from PMS. Labels won't stick to everyone; there are some things that can't be mapped out by an EEG or shoved under the microscope of science and given a common diagnosis. To me, the creative mind and its ability to produce (or lack thereof) is as individual as a fingerprint.
Writers, when you find yourself stalled or driven with your work, what do you think is the main culprit? Or is it different every time?