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Thousand. Before sharing sensitive information, make sure you're on a federal government site. Demographic and substance use characteristics of the sample. The study was conducted in two separate visits.
The first visit included evaluations of the history of substance use and neuropsychological testing. The second visit was scheduled three days after the first and consisted of an MRI. Participants were required to refrain from using MJ and illicit drugs between the two visits so that magnetic resonance imaging and cognitive measures would not reflect the effects of acute poisoning. This resulted in an abstinence period of approximately 72 hours, confirmed by a self-report.
To promote compliance with marijuana abstinence for 72 hours, we follow a false process by testing for cannabis toxicity in urine before and after abstinence (visit 1, visit. While urinalysis is insensitive to 72-hour abstinence, this method has been shown to increase the accuracy of self-reporting (1). Only those who reported having been abstinent for 72 hours were included in the study.). Participants were also asked not to consume caffeine or tobacco for two to four hours before the brain scan and neither of them were allowed during the MRI appointment.
During the second session, each participant underwent an MRI of the head and each was given a brief cognitive battery that included standardized tests for new learning and memory (which are detailed below). One-way ANOVA and paired post-hoc comparisons examined whether the characteristics of the participants differed between the groups (see table). The groups differed in terms of age, IQ, gender, the frequency of excessive alcohol consumption and the number of ADHD symptoms, so subsequent analyses varied simultaneously for these variables. The ratings for mood and anxiety symptoms did not differ by group.
The WMS-III logical memory subtests evaluated the learning and memory of narrative material. Raw Ss%3D scores from immediate memory and recall tests converted into scaled scores normalized to age. Group comparisons were controlled according to IQ, gender, amount of drinks per occasion, symptoms of ADHD, and age. Overall, TBVs were not significantly different between controls, nicotine users, and marijuana users.
Although the memory scores of the MJ users were intermediate compared to those of the Nic and MJ+NIC groups, the differences between the groups in the WMS-III logical memory subtests did not reach significant thresholds. Bivariate scatter diagrams with adjustment lines by group for hippocampal volumes (such as z-score of the TBV ratio) with WMS-III logical memory (a) scaled score for immediate recall (b) and scaled score for delayed recall (b) and scaled score for delayed recall. There are no known studies that have characterized the differential impact between independent use of marijuana and nicotine and the combined use of marijuana and nicotine on brain structure and related functions. In this case, we found that individual and combined marijuana use with tobacco had smaller volumes in the hippocampus compared to tobacco users and controls that did not use it.
We also found differential associations between brain and behavior, so that smaller hippocampal volumes were associated with worse memory performance in controls, while in MJ+NIC users, smaller hippocampal volumes were related to relatively higher memory scores. Our findings on anomalies in hippocampal morphology related to marijuana and their relationship with impaired memory function are consistent with recent findings by Smith and colleagues. The results and conclusions of this study should be examined in the context of its limitations. First, the data set examined in this analysis was derived from two larger main projects, so that certain variables of interest could not be manipulated or controlled to study in more detail the effects related to MJ (p.
ex. Despite these limitations, MJ users (only MJ and MJ+Nic) were homogenous in their use of MJ due to the study's inclusion criteria (almost daily without two or more consecutive days of abstinence from MJ in the previous 90 days). In addition, we only had one common memory measure to examine in our combined sample. Although the WMS-III story memory paradigm is a well-validated and researched instrument, it may not be generalized to learning and memory processes in alternative non-verbal modalities.
In addition, the use of a memory measure with a somewhat greater executive load, such as an unstructured word list learning task, may clarify some of the differential effects of MJ versus nicotine on memory functioning. Finally, the differences between the groups observed in this study were characterized by small to medium effect sizes and future research would be needed to replicate these findings in larger samples. This study provides an important example for the treatment of comorbid substance use in addiction research. Current levels and the possible increase in rates of marijuana and nicotine require a better understanding of their specific and interactive effects (“World Drug Report”, 2010), especially given the likelihood that trends in marijuana use will change with changes in policies.
In the present study, we observed hippocampal volume deficits in MJ users, with even more abnormal brain-behavioral relationships specific to combined MJ+NIC users. As such, the unique neurobehavioral consequences of comorbid tobacco use and MJ have important social and clinical implications. National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894 Web Policies | FOIAHHS Vulnerability Disclosure. The deterioration of cardiovascular function from smoking cannabis or cannabis mixed with tobacco is the result of smoke inhalation.
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