Comparative Study of the Activity of Brain Behavioral Systems in Methamphetamine and Opiate Dependents

Substance dependency is a major problem for the general health of a society. Different approaches have investigated the substance dependency in order to explain it. Gray's reinforcement sensitivity theory (RST) is an advanced and important neuropsychological theory in this area.

The aim of this study was to compare three systems of the revised reinforcement sensitivity theory the behavioral activation system (r-BAS), the revised behavioral inhibition system (r-BIS), and the revised fight/flight/freezing system (r-FFFS) between patients dependent on methamphetamine and opiates, and a group of controls.

This research was a causal-comparative study that was conducted in the first six months of 2012. The population of the study was males of Mashhad city, who were dependent on methamphetamine or opiates, and ruling out psychotic disorders and prominent Axis II. Twenty-five people were selected by the convenient sampling method. Also, 25 non-dependent people from the patients' relatives were selected and matched for the variables of age, gender, and education to participate in this study. Participants were evaluated using a structured clinical interview (SCID) for DSM-IV, demographic questionnaire information, and a Jackson-5 questionnaire (2009). Data were analyzed by Chi-square, K-S, and independent t-test.

The methamphetamine dependent group had a higher sensitivity in the r-BAS, r-BIS, and the r-Fight and r-Freezing systems compared to the control group (P < 0.05). However, there was no significant difference in r-Flight between the two groups (P > 0.05). "The scores of r-BIS were also significantly higher in the methamphetamine-dependent group than the opioid-dependent and control groups. For the r-Fight variable, the methamphetamine-dependent group was higher than the opioid-dependent group".

The personality patterns of patients dependent on methamphetamines were different from the controls. These people have a high sensitivity to punishment cues, such as being compared in social conditions and a tendency for reinforcement and reward, because of their higher sensitivity in the behavioral inhibition and activation systems.