Compulsivity in opioid dependence
This study aimed to investigate the relationship between compulsivity versus impulsivity and structural MRI abnormalities in opioid dependence.Method:
We recruited 146 participants: i) patients with a history of opioid dependence due to chronic heroin use (n = 24), ii) heroin users stabilised on methadone maintenance treatment (n = 48), iii) abstinent participants with a history of opioid dependence due to heroin use (n = 24) and iv) healthy controls (n = 50). Compulsivity was measured using Intra/Extra-Dimensional (IED) Task and impulsivity was measured using the Cambridge Gambling Task (CGT). Structural Magnetic Resonance Imaging (MRI) data were also obtained.Results:
As hypothesised, compulsivity was negatively associated with impulsivity (p < 0.02). Testing for the neural substrates of compulsivity versus impulsivity, we found a higher compulsivity/impulsivity ratio associated with significantly decreased white matter adjacent to the nucleus accumbens, bed nucleus of stria terminalis and rostral cingulate in the abstinent group, compared to the other opioid dependent groups. In addition, self-reported duration of opioid exposure correlated negatively with bilateral globus pallidus grey matter reductions.Conclusion:
Our findings are consistent with Volkow & Koob's addiction models and underline the important role of compulsivity versus impulsivity in opioid dependence. Our results have implications for the treatment of opioid dependence supporting the assertion of different behavioural and biological phenotypes in the opioid dependence and abstinence syndromes.