Each business included in the analyses was verified as being in active operation via phone calls, checking WeedMaps message boards for current ratings and comments, and by whether a dispensary was photographed at that location using Google Street View. Once verified as being active, the address of each storefront was geocoded using geographic information systems software to pinpoint their location within city boundaries and determine their location relative to LA County public high schools. The primary practical use of this research is to establish whether dispensary bans are effective on a city level, or if spillover effects and the many other ways young people can access marijuana render them symbolic. The theoretical relevance is gained by establishing why city dispensary ordinances may or may not be effective. The results of this dissertation will determine whether dispensary bans work by making access less convenient at a city level, by changing teens’ perceptions of risk, or by limiting the number of outlets near areas young people frequent. Research on city dispensary policies and the local impacts of dispensaries on youth use is so scarce that it is unknown if all of these mechanisms apply…or none of them. In this review of the literature I will first assess the physiological, psychological, developmental and social consequences of cannabis grow supplier among adolescents. I will then review the current prevalence of marijuana use as well as trends in attitudes and norms toward marijuana use in California over the past two decades following the legalization of medical marijuana use in 1996. I will then cover current state and local policy approaches to regulating marijuana use and conclude by reviewing gaps in the literature.
Given that the goal of this research is to assess the role of city dispensary policies in limiting exposure to marijuana among adolescents, community and societal-level approaches to marijuana use prevention are the focus of this literature review, rather than family and peer influences.Marijuana and cannabis are used as general terms to refer to the many extracts and preparations that can be made from this plant. Marijuana products vary in effects and potency by genetic strain, cultivation technique, and by how it is processed . Traditionally used by smoking the dried flowers, marijuana can also be used by heating flowers, oils, or other concentrated forms in electronic vaporizing devices, by baking extracted oils into foods, and in pills, tinctures, sprays, creams, ointments, eye drops, and suppositories . The chemical contents of marijuana include over 100 cannabinoids; chemical compounds with physiological and/or psychoactive effects. The distinct effects of most cannabinoids have yet to be studied in laboratory settings and are poorly understood . The two best-known cannabinoids are delta-9 tetrahydrocannabinol and cannabidiol . THC is the primary psychoactive ingredient in marijuana that causes intoxication and euphoria. CBD is thought to be responsible for the anti-convulsive and pain-relieving properties of marijuana but is not intoxicating. Recent research on therapeutic uses of cannabinoids has shown that they have considerable promise to treat appetite loss, nausea, chronic pain, insomnia, inflammation, and glaucoma , but marijuana products containing THC also produce potent psychoactive side effects. Favorable psychoactive effects from THC include calming, relaxing, stimulating, or uplifting feelings, but unpleasant effects like anxiety, panic attacks, and paranoia can also occur . THC products act on the central and peripheral nervous systems by binding to receptors for endogenous cannabinoids called “endocannabinoids”.
Endocannabinoids are neurotransmitters naturally produced in the human brain that bind to and activate cannabinoid receptors found in the prefrontal cortex, hippocampus, basal ganglia, thalamus, hypothalamus, and cerebellum . The psychoactive effects of marijuana are produced by displacing endocannabinoids with exogenous cannabinoids such as THC, thus altering cognitive function. Documented effects of marijuana use on cognitive function include chronic short-term memory problems, loss of balance and coordination, difficulty concentrating, changes in sensory perceptions, impaired ability to perform complex tasks, decreased alertness, and decreased reaction time . Long-term cognitive effects from marijuana use are mild compared to those described above but can last for weeks after acute effects wear off . The most enduring cognitive effects are seen in decision-making, concept formation, and planning . Cognitive effects also differ in severity depending on the quantity of regular use, how recently a person used, how old they were when they started using marijuana, and how long they have been using it . Marijuana use that occurs during adolescence has been associated with use of other drugs , poor school performance, and a higher likelihood of substance abuse or dependence in adulthood . Adolescents are more vulnerable to harmful effects from marijuana use because of the active processes of brain development that occur during this stage . For example, developing dependence on marijuana is more likely among adolescents than among adults and the effects of frequent use at this age appear to be much longer lasting. The overall likelihood of developing dependency among people who use marijuana is estimated to be 9% , but among people who begin using marijuana before age 18, the likelihood to develop dependence is almost doubled and developing symptoms of problem use is estimated to be 4 to 7 times more likely .
Among adults the cognitive effects of marijuana use generally disappear within a month, when the last traces of the fat-soluble THC molecule dissipate . In contrast, neuroimaging studies have shown that regular marijuana use in adolescence is associated with changes to areas of the brain involved in executive functions like memory, attention, learning, retention, and impulse control . Advances in brain imaging technology have made it possible to directly observe the impact of substance use on the brain ,cannabis drainage system which has resulted in a greater understanding of the mechanisms by which marijuana use interferes with normal brain development. Studies using prospective case-control and other longitudinal designs have found that cognitive effects from repeated marijuana use during adolescence persist into adulthood . Windle and colleagues recently reported results from a prospective study that followed U.S. children into adulthood where they found that substance use between the ages of 13 and 15 years old was associated with a smaller amygdala, a brain region that develops earlier in adolescence and is crucial to emotional regulation. The authors also found that substance use between the ages of 16 and 18 years old was associated with a lower volume of gray matter in the pars opercularis, a region of the brain that develops later in adolescence and is responsible for cognitive control. These very recent research findings suggest that not only does substance use during adolescence result in changes to the brain that persist into adulthood, but that initiating regular use at different times may affect different regions of the brain according to which regions are in active development at the age when the substance use is occurring. Recent research has documented that endocannabinoids are instrumental to the final processes of brain development that occur during adolescence . Receptors for endocannabinoids begin to increase in the subcortical and frontal cortical regions of the brain during childhood and peak in adulthood, which has led scientists to conclude that the endocannabinoid system is a mechanism through which greater degrees of cognitive control are achieved between childhood and adulthood . During normal neural development endocannabinoid receptors are pruned as part of the consolidation of neuronal pathways that increases efficiency in signals to and from the prefrontal cortex, which in turn increases the capacities for cognitive control and self-directed behavior . If THC molecules replace the endocannabinoids that drive these processes, it alters the way the brain consolidates neuronal pathways throughout adolescence, which may in turn result in less capacity for cognitive control and self-directed behavior in adulthood . The Dunedin Longitudinal Study, a prospective cohort study conducted in Dunedin, New Zealand, has provided the best evidence of the long-term effects of marijuana use on intelligence and life prospects. In this study, 1,037 people were followed from birth into adulthood. Their intelligence was assessed at the ages of 7, 9, 11, and 13 years of age using the Intelligence Quotient test .
The Dunedin Longitudinal Study investigators found that repeated marijuana use before the age of 15 years old was associated with declines across multiple domains of cognitive functioning, even after controlling for years of education . Their research was the first to document a decline in cognitive functioning from adolescence to adulthood among adolescent-onset marijuana users compared to non-users and that cessation of marijuana use after adolescence did not fully restore neuropsychological functioning in adulthood. More recently, Cerda and colleagues used the Dunedin Longitudinal Study data to demonstrate that chronic marijuana use during adolescence and adulthood was associated with downward socioeconomic mobility and more financial difficulties, and workplace problems in early midlife, even when controlling for socioeconomic adversity, childhood psychopathology, achievement orientation, family structure, marijuana-related criminal convictions, early onset of marijuana dependence, and comorbid substance dependence. The threshold of adolescent marijuana use where loss of cognitive potential occurs or where dependence becomes a risk is unknown and likely differs by individual. Nevertheless, it is clear from the literature that earlier and more frequent marijuana use during childhood and adolescence is associated with a greater potential to disrupt normal brain development and to develop problem substance use . More randomized controlled trials and prospective cohort studies are needed to definitively characterize the impacts of marijuana use on adolescent brain development, but the current body of literature persuasively documents the importance of minimizing exposure to THC during adolescence . The 2017 National Survey on Drug Use and Health Annual Report indicates that 25% of 9th graders and 37% of 11th graders in the U.S. report lifetime marijuana use, while 13% of 9th graders and 18% of 11th graders in the U.S. report having used within the past 30 days . The Monitoring the Future study found that as of 2017, 6% of 12th graders in the U.S. report daily use of marijuana, which corresponds to about one in 16 high school seniors . Rates of recent marijuana use among adolescents in California are over three times higher than the national average; 22% of California adolescents aged 12-17 reported using marijuana in the past 30 days in 2017 , compared to 6.5% nationally . NSDUH trend data for California between 2002 and 2014 indicates that among youth aged 12-17 there has been an overall increase of 16%, but also that there was not a consistent trend of increase. Instead, marijuana decreased from the 2002-2003 study years through the 2005-2006 study years and held relatively steady before increasing again during the 2010-2011 study years . A Community Needs Assessment conducted by the LA County Department of Public Health in 2017 indicates that nearly half of LA County residents aged 12 or older have used marijuana at least once in their lifetime and that 14% had used marijuana in the past 30 days. It also found that residents were an average age of 17 years old when they first used marijuana, with a majority using marijuana for the first time before age 18. Similar to national and state reports of the perceived accessibility of marijuana, the LA County assessment found that most County residents over the age of 12 perceived it easy to access marijuana in their neighborhood. The marijuana users in the study most commonly obtained their marijuana from a friend , followed by a dispensary , family/relative , or the illicit market . More specific data is available from the YRBSS survey for the Los Angeles Unified School District and indicates a local pattern different from what has been observed at a state level . Changing attitudes to perceive marijuana use as more socially acceptable and less of a health risk have been noted among youth populations, but whether changes in these attitudes are the result of policy changes or of a general secular change in attitudes toward marijuana is often difficult to determine. Some research supports the idea that the increasingly liberal state laws governing marijuana in the U.S. stem from more positive adult attitudes toward marijuana rather than the reverse. For example, rates of marijuana use among adults is higher in states that have approved medical and recreational marijuana laws, but the higher rates of marijuana use in these states preceded enactment of the laws, suggesting that the more liberal attitudes toward marijuana use were a motivation for liberalizing marijuana laws .