Often masked by the bulimia itself, dysthymia - a lower-level, chronic form of depression - is often present in bulimics and may even predispose them to the eating disorder, shows the research by Perez and her colleagues Thomas E. Joiner Jr. of Florida State University and Peter M. Lewinsohn of the Oregon Research Institute.
Dysthymia, Perez explains, is different from the more familiar major depression in terms of its duration, severity and persistence of mood disturbance, all factors that can impact the course and treatment of eating disorders.
"As pernicious as major depression can be, it tends to remit, even if untreated," she notes. "By contrast, dysthymia is unrelenting, often lasting decades, with the average episode length lasting more than 10 years."
It's this long-lasting nature, Perez says, that makes dysthymia, rather than major depression, more likely to be associated with bulimia, which is characterized by unrelenting negative feelings about one's self.
Bulimics, she says, tend to have chronic low self-esteem. Previous models, she notes, have proposed that high perfectionism when dashed by low self-worth is predictive of bulimia. Because of this, the chronic and pervasive self-esteem problems associated with dysthymia may make dysthymic people vulnerable to bulimia, she says.
The relationship between bulimia and dysthymia might be the struggle to regulate unrelenting negative moods stemming from the depression and the feelings of low self-esteem associated with the eating disorder, Perez speculates.