Insulin but not insulin growth factor-1 correlates with craving in currently drinking alcohol-dependent patients

Background: Preclinical data suggest that brain insulin and insulin growth factor-1 (IGF-1) may contribute to the development of addiction. The aim of this clinical study was to evaluate the relationships between insulin and IGF-1 plasma concentrations and alcohol craving. Methods: The correlations between insulin and craving in actively drinking alcoholics were evaluated in the experiment 1 retrospectively and in the experiment 2 in a case-control study. Experiment 3 evaluated the correlations between insulin and craving in 12-weeks abstinent alcoholics in a longitudinal study. C-peptide and IGF-1 were also investigated in experiments 2-3. Alcohol craving was evaluated by the Obsessive-Compulsive Drinking Scale (OCDS). Results: Significant positive correlations between insulin concentrations and craving scores were found in actively drinkers (p < 0.05). Specifically, in the first experiment insulin significantly correlated with the compulsive scores. In the second experiment and in an analysis of experiments 1-2 together, insulin plasma concentration correlated with total OCDS craving (p < 0.05) and compulsive craving (p < 0.05) and showed a trend of correlation with the obsessive craving. At 12 weeks no correlation was found between insulin and craving scores. In all the experiments the correlations between C-peptide and craving were close to the ones between insulin and craving while IGF-1 never correlated with craving. Conclusions: This study suggests that insulin could be involved in the neurobiology of alcohol craving and addiction. This characteristic seems specific of insulin since similar data were found on C-peptide but not on IGF-1. Future confirming studies on larger samples are needed, also to investigate possible therapeutic implications.