In mammals, the suprachiasmatic nuclei of the hypothalamus contain the master circadian clock that coordinates the daily temporal organization of endogenous rhythms. The core oscillation is thought to be driven by several genes called “clock genes” for their crucial role in the clockwork. Eating disorders (EDs), such as anorexia nervosa (AN) and bulimia nervosa (BN), are characterized by a disruption of circadian feeding patterns, as well as by alterations in the circadian rhythms of endogenous hormones. Therefore, a possible role of the clock gene in the biological vulnerability to EDs may be suggested.

To explore this hypothesis we designed a case-control study study exploring the 3111T/C polymorphism of the CLOCK gene in patients with EDs. One hundred fifty one female Caucasian patients were enrolled into the study. Sixty of them met the DSM-IV diagnosis of AN and 91 met the DSM-IV diagnosis of BN purging. A group of 90 normal weight Caucasian healthy women were also recruited. We could not detect any significant association between the 3111T/C polymorphism of the CLOCK gene and AN or BN. Moreover, we found that the 3111T/C polymorphism of the CLOCK gene was significantly associated with minimum past BW in both AN and BN individuals, but not in healthy controls.

In conclusion, our present findings, although preliminary, suggest that the CLOCK 3111T/C SNP does not represent a major vulnerability factor for AN and BN, but seems to predispose ED patients to a more severe BW loss in the course of their illness.