FDG-PET study in pathological gamblers: 1. Lithium increases orbitofrontal, dorsolateral and cingulate metabolism

Background: Pathological gambling affects 1-3% of the adult population, and has high comorbidity. Although mood stabilizers and serotonin reuptake inhibitors have shown some efficacy in the treatment of this condition, there is little known about how these pharmacological interventions work. Methods: Twenty-one patients with pathological gambling, who met lifetime comorbid bipolar spectrum diagnoses, received baseline PET scans. Sixteen of these patients were entered into a randomized double-blind placebo-controlled parallel group design trial of lithium, and received follow-up PET scans at 10 weeks. A comparison group of 32 age- and sex-matched controls was also available. Anatomical MRIs were obtained as a structural template. Results: In patients with pathological gambling, relative glucose metabolic rates (rGMR) in the orbitofrontal cortex and medial frontal cortex were significantly increased at baseline compared to normal controls. Lithium increased rGMR further in the orbitofrontal cortex, heightening normal/patient differences, but it also increased the rGMR of the posterior cingulate and the dorsolateral frontal cortex normalizing the metabolic rate in these regions. Conclusion: Cortical areas implicated in impulse control disorders show increased rGMR in pathological gambling at baseline. Lithium treatment, while alleviating the symptoms, further increases rGMR in these areas.