Neurobiological and psychopathological variables related to emotional instability: a study of their capability to discriminate patients with bulimia nervosa from healthy controls.

OBJECTIVE: To analyze the capability of a set of neurobiological and psychopathological variables to discriminate bulimia nervosa (BN) patients from healthy controls. METHOD: Seventy-five female patients with purging BN and 30 healthy controls were compared for psychopathology (impulsivity, borderline personality traits, depressive symptoms and self-defeating personality traits) and neurobiological parameters reflecting hypothalamic-pituitary-adrenal axis activity (morning serum cortisol before and after dexamethasone) and monoamine activity (24-hour urinary excretion of norepinephrine, serotonin, dopamine, and their main metabolites: 3-methoxy-4-hydroxyphenylglycol, 5-hydroxyindoleacetic acid, and homovanillic acid). Furthermore, the relationships between the 2 sets of variables were compared in the 2 samples. RESULTS: BN patients displayed higher impulsivity, more severe depressive features, and more borderline and self-defeating personality traits than controls. The 4 psychopathological variables were strongly interrelated in patients, whereas only depressive features correlated with self-defeating personality traits in controls. Patients had lower 24-hour excretion of serotonin and dopamine than controls, as well as lower ability to suppress cortisol. The relations between the biochemical and the psychopathological variables were only significant in the BN patients, but not in the control group. When discriminant analysis methods were applied, patients and controls differed for psychopathology (impulsive behaviors and borderline personality traits) and biological parameters (baseline cortisol and dopamine excretion), but when the variables were analyzed together, the differences in neurobiological parameters appeared as mediated by the psychopathological status. DISCUSSION: Our results suggest that hypothalamic-pituitary-adrenal axis activity, dopamine activity and other biological parameters are worthy of further study as potential dimensional markers of BN, although they seem to depend on the psychopathological status of the patients, in such a way that the psychopathological items associated with emotional instability (impulsivity and borderline personality traits) seem to be more reliable as clinical markers at the time being.