Brain dysfunction differs in addicts to inhaled and smoked cocaine. Implications for aggressive behavior

Objectives To assess the difference in brain dysfunction between chronic active consumers of smoked and inhaled cocaine and evaluate correlations with aggressive behavior.

Methods 21 chronic active users of cocaine basic paste (smoked cocaine containing about 70% of cocaine base), 18 inhaled cocaine chlorhydrate (IC) users and 23 normal controls (NC) were studied at rest with 99mTc-ECD SPECT. Age and gender did not differ statistically between groups (range 18-35 ys). Concomitant use of marijuana, alcohol and BZD was present in both groups in similar proportions. SPM5 was used to compare both groups with NC. Uncorrected voxel p values below 0.01 were reported, and clusters containing more than 100 voxels. Presence or absence of verbal or physical heteroaggressive behavior or autoaggressiveness was entered as a covariate in the analysis.

Results Smoked cocaine (SC) users showed bilateral dorsolateral prefrontal (DLPF), dorsal and ventral mesial frontal (MF) and anterior cyngulate hypoactivity, as well as mesial and anterobasal temporal, posterior parietal, thalamic and midbrain hypoperfusion. IC users showed more limited hypoperfusion in right DLPF, bilateral anterior MF and posterior parietal cortex. Aggressive behavior was present in 61.1% of IC users and 71,5% of SC users. Correlations were found in bilateral DLPF, dorsal MF and posterior parietal cortex of IC users but not in SC ones.

Conclusions Greater prefrontal and lymbic hypoactivity characterized SC consumption, reflecting pronounced dysfunction of the reward system responsible for the more severe dependence to SC than IC. These findings may also account for the grater predisposition to aggressive and violent acts of SC users. Dysfunction of the prefrontal inhibitory system was associated with aggressive behavior in IC users but not in SC users, probably because most of them presented this kind of behavior as well as severe dysfunction of the related structures. Next step is to look for correlations with aggression scales