Use of alcohol, cannabis and opioids is highly prevalent and is associated with global disease burden and high economic costs. The exact pathophysiology of abuse or addiction associated with these sedative substances is not completely understood, but previous research implicates the important role of the striatal dopamine system in the addiction process. Multiple studies investigated changes in the striatal dopamine systems of users of sedative substances, but currently these results are very heterogeneous. Therefore, we conducted a meta-analysis of in vivo neuroimaging studies investigating dopaminergic alterations in the striatum of users of alcohol, opioids or cannabis. Analyses for each substance were conducted separately for the availability of D2/D3 dopamine receptors, dopamine transporters and dopamine synthesis capacity. In total, 723 substance users and 752 healthy controls were included. The results indicated a significant lower striatal D2/D3 receptor availability in alcohol users compared to controls (g = 0.46) but no difference in dopamine transporter availability or dopamine synthesis capacity. Our analysis indicated that changes of dopamine receptors and transporters are moderated by the duration of abstinence. Comparing opioid users with controls revealed a significant lower D2/D3 receptor availability (g = 1.17) and a significantly lower transporter availability (g = 1.55) in opioid users. For cannabis users, there was no significant difference in receptor availability compared to controls and too few studies provided information on dopamine transporter availability or synthesis capacity. Our analysis provides strong evidence for a central role of the striatal dopamine system in use of alcohol or opioids. Further studies are needed to clarify the impact of the dopamine system in cannabis users.

Background:Stimulant drugs can cause persistent changes in the brain. Imaging studies show that these changes are most apparent in dopamine transporter (DAT) or receptor availability within the striatum.Methods:This work focuses on influences of stimulant use on dopaminergic function assessed using nuclear-medicine imaging (PET/SPECT). Included are 39 studies on 655 cocaine, amphetamine, methamphetamine or nicotine users, as well as 690 healthy controls. Metaanalyses were conducted separately for D2/D3 receptors and dopamine transporters of the entire striatum, its subregions caudate and putamen respectively.Results:Meta-analyses results regarding nicotine did not show significant effects between smokers and nonsmokers. In cocaine users there was a significant decrease in dopamine receptor availability in all regions. The striatal DAT availability was significantly increased in cocaine users. Methamphetamine users showed a significantly decreased dopamine receptor and transporter density in all regions. Significant results also indicate a lower transporter availability in all regions. Amphetamine users showed reduced DAT availability in the striatum, as well as in the sub regions.Conclusion:This meta-analysis provides evidence that there are ongoing changes in the dopaminergic system associated with the use of stimulants. Especially the results of cocaine, methamphetamine and amphetamine use mainly showed a downregulation. In addition, this meta-analysis is the first to include nicotine. This subset of studies showed evidence for a decreased receptor and DAT availability but no significant results were found in the metaanalyses.

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Methamphetamine use has spread in many European countries and the United States. The current review provides a summary and critical analysis of research on cognitive deficits associated with methamphetamine, also known as "crystal meth." The literature search performed for this review led us to the hypothesis that methamphetamine use is associated with persistent changes in brain metabolism that result in various impairments, such as deficits in memory, attention, and concentration. The dopaminergic system in particular seems to be affected. Some studies indicate that cognitive impairments may improve when users become abstinent, but results of other studies are conflicting. This review discusses these findings and the consequences for the development of a specific addiction treatment for methamphetamine.

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Methamphetamine use disorder is associated with severe psychiatric symptoms and psychosocial problems. Women seem to be more affected than men. Therefore, this study examined psychiatric comorbidities and psychopathology, drug use patterns, and treatment outcomes in women addicted to methamphetamine compared to men. Data on methamphetamine-dependent inpatients were collected in two centers specialized for addiction treatment at admission (T0) and discharge (T1, after treatment for 24 weeks). Sociodemographic and clinical measures were collected with the semi-structured clinical interview I at baseline; the self-reported standardized questionnaire (SCL-90-R) was administered at admission and discharge and after 24 weeks. During the entire treatment procedure, treatment relevant aspects were monitored. Out of all 108 treatment-seeking participants (86 men, 22 women), 64 completed the study (51 men, 13 women; drop-out rate: 40.7% (n = 44)). Methamphetamine-dependent women used other stimulants more often than men, while men used hallucinogens significantly more frequently than women. Female inpatients differed significantly from men in various sociodemographic variables (e.g., having children, single parenting) and were significantly more often affected by current (p < 0.001) and lifetime mental stress disorders (p < 0.001), as well as specific psychiatric disorders (p < 0.001) (e.g., posttraumatic stress disorder). At discharge, mental symptoms decreased significantly in men but not in women. Both before and after treatment, women seem to be more vulnerable to psychiatric comorbidities and psychopathologic symptoms compared to men. Although this study only provides preliminary data on gender-specific characteristics of methamphetamine-dependent patients and their treatment, it seems appropriate to discuss the development of gender-specific treatment options. Further studies in this field are needed.