Rationale: Translational research implicates the mu opioid neurochemical system in hedonic processing, but its role in dissociable high-level cognitive functions is not well understood. Binge-eating represents a useful model of 'behavioural addiction' for exploring this issue.
Objective: The aim of this study was to objectively assess the cognitive effects of a mu opioid receptor antagonist in obese individuals with binge-eating symptoms.
Methods: Adults with moderate to severe binge-eating and body mass index ≥30 kg/m² received 4 weeks of treatment with a mu opioid receptor antagonist (GSK1521498) 2 or 5 mg per day, or placebo, in a double-blind randomised parallel design. Neuropsychological assessment was undertaken at baseline and endpoint to quantify processing bias for food stimuli (visual dot probe with 500- and 2,000-ms stimulus presentations and food Stroop tasks) and other distinct cognitive functions (N-back working memory, sustained attention, and power of attention tasks).
Results: GSK1521498 5 mg/day significantly reduced attentional bias for food cues on the visual dot probe task versus placebo (p = 0.042), with no effects detected on other cognitive tasks (all p > 0.10). The effect on attentional bias was limited to the longer stimulus duration condition in the higher dose cohort alone.
Conclusions: These findings support a central role for mu opioid receptors in aspects of attentional processing of food cues but militate against the notion of major modulatory influences of mu opioid receptors in working memory and sustained attention. The findings have implications for novel therapeutic directions and suggest that the role of different opioid receptors in cognition merits further research.