Information and Statistics - Bulimia Nervosa

Bulimia Nervosa meanwhile was first described in 1979 by Gerald Russell, and was described as 'an ominous variant of anorexia nervosa.'  It was added as a diagnostic criterion in 1980.  It is estimated to affect 1-3% of adolescent/young adult women.  The average age of onset is slightly higher than Anorexia (median reported is 18 yrs).  The actual rates of Bulimia Nervosa are hard to estimate as studies have shown that the majority of cases go unreported and un-treated. 
 
Some studies suggest up to 40% of cases of anorexia will eventually develop some form of bulimia.
 
Purging behaviour in Bulimia Nervosa is often learned - ie the sufferer, already experiencing out of control binges, one day tries something that s/he believes will stop them from absorbing the food they have eaten/stop them from putting weight on.  Adding this purging stage then makes binges worse because swallowing food is no longer a 'point of no return' - they now believe there is something they can do afterwards, so control breaks down even further. 
 
Rates of Bulimia seem to vary over the years - raising suggestions that it is to some degree a culturally controlled phenomenon (more so than anorexia).