Computer IP addresses were tracked in the study. If the respondent’s computer indicated that the survey had already been completed, the Qualtrics system would not allow the participant to regain access to the survey. Participants’ contact information was stored in a separate file unlinked to survey responses and destroyed immediately following the study. Identifiable research information was protected by a Certificate of Confidentiality from the National Institutes of Health. All materials and procedures were approved by the Institutional Review Board at the University of Cincinnati.The Nicotine and Marijuana Interaction Expectancy questionnaire is a 14-item measure designed to examine client’s perceptions of the interaction between cigarettes and marijuana. Participants rated each of the items on a Likert scale ranging from 1 to 5 . The NAMIE includes three scales: the effects of marijuana use on cigarette smoking ; the effects of cigarette use on marijuana smoking ; and smoking cigarettes to cope with urges to use marijuana . Participants’ tobacco and marijuana history and use were assessed using items from the National Survey on Drug Use and Health . Tobacco use measures included age of first tobacco use, days of past month tobacco use, type of cigarettes smoked and use of other tobacco products . Marijuana use measures included age of first use, days of past month marijuana use and days of past month blunt use. Participants who reported past month blunt use and cigarette use were categorized as “blunt co-users”, while participants who reported cigarette use but no past month blunt use were categorized as “non-blunt co-users.” The survey also assessed past month use of other drugs,commercial plant racks including cocaine, opioids, and alcohol.Descriptive statistics and Cronbach’s alpha coefficients were estimated to characterize the sample and examine the reliability of the NAMIE sub-scales among African American young adults.
Six multiple regression models examined the relationship between each of three NAMIE sub-scales and marijuana use and initiation and tobacco use and initiation.To control for multiple comparisons but allow for meaningful patterns to emerge from the data, significance level was set at .01. The sample was mostly male and had an average age of 23.7 . Most participants were college graduates and had full-time jobs . Approximately 49% of the sample reported legal trouble. Cigars, cigarillos, and little cigars were the second most popular tobacco product used in the past month following cigarettes . Participants also reported smoking menthol cigarettes and drinking alcohol in the past month. The majority of the sample also reported smoking blunts in the past year , and in the past month . In the month preceding the study, participants reported smoking marijuana for an average of 12.6 days and tobacco for an average of 20.4 days. As shown in Table 1, relative to non-blunt co-users, blunt co-users were more likely to have some college experience or be a college graduate and reported drinking alcohol in the past month. The current study examined the interaction expectancies of African American young adults who reported marijuana and cigarette use in the past month. Expectations regarding the interaction of marijuana and tobacco as measured by the NAMIE showed strong internal consistency, supporting use of this measure in the African-American population. Reliability compares to that among a predominately White sample of marijuana and tobacco co-users participating in a national online survey ; however mean scores were relatively higher in the current study compared to the Ramo et al study on all three NAMIE scales. It is unclear whether the scores are statistically different across groups. This could not have been accounted for solely by the extent of blunt use in this African-American sample, as scores were higher for non-blunt co-users in the current study as well. More work is needed to clarify ethnic differences in interactions expectancies more fully.
African American young adults reported the highest rating on scale 1 , which might partially explain why tobacco initiation often follows marijuana use among African American young adults . Longitudinal research is needed to examine the relationship between co-use expectations and marijuana and tobacco initiation among African American young adults. Relative to blunt co-users, non-blunt co-users were more likely to report that smoking cigarettes increased their marijuana use and urges and that smoking cigarettes helps them to cope with their marijuana use and urges. Blunt smokers are exposed to nicotine when preparing blunts with the outer wraps of cigars and cigarillos , while non-blunt marijuana users are not exposed to nicotine in the same way. Non-blunt co-users might lean more heavily on cigarettes for exposure to nicotine and therefore may be more likely to believe that cigarettes have a more powerful role in the interaction between marijuana and tobacco. It might follow that nonblunt co-users would smoke more cigarettes than blunt co-users, however, findings here do not support that notion. It is important to note that all of the participants in this sample reported 20 or more days of past month tobacco use, and 87.2% reported smoking menthol cigarettes in the past month, consistent with other African-American smoking samples . Additional research with a wide range of light and heavy menthol and non-menthol cigarette smokers is needed. Notably, we found that days of past-month marijuana use were associated with co-use expectations among blunt co-users but not among other co-users. This could indicate that the NAMIE is a better assessment tool for blunt co-users than non-blunt co-users, or that substituting tobacco for marijuana and vice-versa is equally common among non-blunt cousers of all levels. Research with larger samples is needed to clarify this further. In addition to a small sample size, there are a few other limitations that should be noted. First, the cross-sectional design of the study prevents causal interpretation of the findings. Second, the sample is mostly male and may not be generalizable to a more diverse sample of African American young adults.
The study relied on self-reported, anonymous data; however, the targeted recruitment method increases the validity of the data. Despite these limitations, the current findings highlight preliminary evidence for the significant relationship between drug use outcomes and co-use expectancies among African American young adults that has important research and clinical implications. Our findings highlight the extent to which tobacco and marijuana use can perpetuate use of the other substance, and the importance of treatments targeting thoughts and expectations about the interaction of these two substances. Understanding the relationship between marijuana and tobacco will increase the effectiveness of existing interventions and facilitate the development of new interventions that target cognitions related to co-use among African American young adults, especially among individuals who co-use cigarettes and blunts.Marijuana is commonly used in adolescence, yet the impact on the developing brain is unclear. Working memory impairments have been observed in adult marijuana users after recent use, but may remit after a month of abstinence. The differential effects related to recent use and abstinence have not been delineated in adolescents. To address this question, three studies examined functional magnetic resonance imaging brain response during spatial working memory among adolescents.Adolescent brain development may be influenced by heavy marijuana use, yet the neural underpinnings of SWM have not been well described in adolescents. Study 1 investigated fMRI response to SWM across normal adolescent development. Participants were 49 youths ages 12 – 17 without histories of neurological or psychiatric disorders. Results demonstrate the emergence of left prefrontal activity and superior-to-inferior shift in localization of parietal response with increasing age, suggesting that younger teens utilize more rote spatial rehearsal,ebb and flow tray while older teens rely more on spatial storage and verbally-mediated strategies. Study 2 evaluated fMRI response during SWM among 15 heavy marijuana using adolescents after 28 days of verified abstinence relative to 17 non-abusing controls, ages 16 – 18 years old. Marijuana users demonstrated decreased right prefrontal and increased right superior parietal response relative to controls, which could suggest greater reliance on spatial strategies and less general executive control among marijuana users. These results were observed after 28 days of abstinence, suggesting persisting differences in brain functioning among heavy marijuana users. Study 3 characterized the differential residual and persisting changes in neural activation patterns associated with adolescent marijuana use by examining fMRI during SWM among adolescent marijuana users after recent use or after one month of abstinence.
Participants were 15- to 18-year-olds: 13 marijuana users who used in the week before scanning, 13 marijuana users who were abstinent for 27 – 60 days before scanning, and 18 demographically similar controls. Recent users demonstrated increased medial/left superior frontal and right parietal response relative to abstinent users, which could suggest greater neural effort for inhibitory control and spatial rehearsal. Although cross-sectional, results may indicate a shift in neural processing strategies through early abstinence.Marijuana is the most commonly used illicit drug among teenagers, and most users first try marijuana in adolescence . While 17% of 8th graders have tried marijuana, almost half of 12th graders have used cannabinoids . Frequency of use escalates so that by 12th grade, 20% report past-month use and 5% reveal daily use . During this period of increasing marijuana use, the brain remains in an active state of development, characterized by synaptic refinement , myelination , and improved cognitive and functional efficiency . In particular, working memory abilities improve throughout childhood and adolescence as the brain regions sub-serving these functions mature. Yet working memory may be adversely impacted by marijuana use, as marijuana most likely affects frontal and parietal brain regions involved. Given continued development of these systems in adolescence, heavy marijuana use during youth could negatively impact working memory functioning. The possible influence of marijuana use in adolescence and the potential for recovery with abstinence have not been well delineated, but could have important implications for academic, occupational, and social achievement among both current and former users. This dissertation aims to characterize the influence of chronic marijuana use on functional magnetic resonance imaging brain response during spatial working memory in adolescents through the completion of three studies. In order to understand the effects of chronic marijuana use in youth, a better depiction of neural response patterns in normal adolescents is needed. To this end, Study 1 investigated fMRI response to SWM across normal adolescent development. Study 2 then evaluated fMRI response during SWM among heavy marijuana using adolescents after 28 days of verified abstinence relative to non-abusing controls. Finally, Study 3 characterized the differential neurocognitive impact of recent adolescent marijuana use relative to the potentially persisting effects by examining fMRI during SWM among adolescent marijuana users within one week of use or after one month of abstinence. The results of these three studies provide a better understanding of the neural impact of heavy marijuana use during adolescence.Modern neuroimaging techniques have a provided a wealth of information about human brain development. Whereas it was once believed that the human brain was largely developed by the onset of puberty, it has now been established that the brain continues to develop throughout adolescence and well into adulthood . A recent longitudinal investigation demonstrated that higher order association cortices, such as superior temporal, posterior parietal, and prefrontal cortex, develop later than primary sensorimotor cortices, with the dorsolateral prefrontal cortex developing last . This late occurring development is predominantly a function of the progressive and regressive processes of myelination and synaptic pruning that result in increasing white matter volumes and cortical thinning and a more efficient central nervous system. During adolescence and this time of active neural maturation, many cognitive processes are also developing. One such process is working memory. Working memory refers to the ability to actively store and manipulate information online over brief periods of time . This ability is fundamental to intact performance in a variety of other cognitive domains, including language comprehension, abstract reasoning, and learning and memory . Verbal and spatial working memory abilities improve throughout childhood and adolescence , with accuracy and reaction times increasing and decreasing respectively during spatial n-back and spatial delayed response tasks . It is likely that these behavioral improvements in working memory are the result of the described neuromaturational processes that are occurring during the child and adolescent years. With the advent of functional magnetic resonance imaging , the neural substrates of working memory functioning have begun to be identified.