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.