The Impact of Marijuana on Mental Health

The association between marijuana use and several mental health outcomes is examined, with particular reference to commonly held views on the lack of proof for a causal basis. Rather than relying on a single, key criterion for proof of causation, a collective approach is taken to the question through reviewing studies testing different criteria. Exploration of the psychiatric epidemiology on marijuana reveals trends in early reports that have been confirmed through more detailed studies in recent years and further bolstered by clinical findings. A significant, causal role for marijuana use in chronic psychotic disorders is substantiated by the literature, as well as a strong association with mood disorders and suicidal behaviors. This chapter reinforces the importance of considering marijuana’s mental health impacts when formulating appropriate public health programs and when fashioning drug control policies concerning its legal status.

Policy Implications

This chapter reviews policy implications associated with legalizing marijuana for medical and recreational purposes. The authors discuss the current landscape and attitudes toward marijuana use and review the enforcement polices of the federal government, including the impact of policies within the United States Department of Justice and the United States Government Accountability Office. The chapter also examines the expanding marijuana industry and warns against the growth of ‘Big Marijuana’ and the industry’s ability to influence policy. Finally, after reviewing the important pros and cons of legalizing this drug, the authors offer several guidelines for states to optimize care when legalization is implemented.

Risk Factors for Adolescent Marijuana Use

Marijuana use has been linked to a wide variety of negative consequences, especially for those who initiate use in early adolescence and become daily or regular users as a teenager. If these negative consequences are to be avoided, prevention efforts must focus upstream on childhood and adolescent developmental periods before marijuana use is initiated or has become frequent. Upstream prevention targets factors that predict initiation and escalation of marijuana use, which are often called risk and protective factors. This chapter provides a review of current knowledge about risk and protective factors, with an emphasis on psychosocial variables specific to marijuana, differentiating predictors of marijuana use from predictors of other legal and illegal drugs when possible. The chapter also provides suggestions for future research in light of the rapidly changing legal and community conditions related to access, availability, and norms of marijuana use.

International Trends in Cannabis Use

This chapter focuses on international trends. Mainly, the chapter provides estimates that illustrate generally stable recent trends in the frequency and occurrence of use in most countries for which survey data have been distributed, with some noteworthy exceptions to this stability. The chapter offers a first approximation of a global tour of cannabis smoking estimates and trends and covers evidence on the hypothesized possibility of a narrowing of the male–female difference in risk of becoming a cannabis user. The chapter closes with thoughts on an International Cannabis Products Safety Commission that is needed to keep track of trends and to investigate hypotheses about psychoses and other hazards attributed to consumer end-user ingestion of cannabis products.

Marijuana-Impaired Driving

Drug-impaired driving is a serious threat to public safety and health on par with alcohol-impaired driving. Marijuana is the most widely used illicit drug among drivers, including those seriously and fatally injured in crashes. Research confirms that marijuana use can cause significant short- and long-term impairment, putting users and others on the road at risk of crash and injury. There is no consistent relationship between the blood concentration of ∆9-tetrahydrocannabinol, the primary psychoactive component in marijuana, and driving impairment. There is substantial precedent and support for zero tolerance per se laws for drugs for drivers arrested for suspicion of driving under the influence. Administrative license revocation is another tool currently used in alcohol-impaired driving cases that could be useful for removing drug-impaired drivers from the road. Recommendations are provided for drug testing, including using new oral fluid screening technology and further research on and monitoring of marijuana-impaired driving.

Introduction

Marijuana policies and the plant itself have been changing in recent years. With respect to polices, many regions internationally now have decriminalization policies, and, as is the case in the United States, many states have legalized it for either medical or recreational purposes. The marijuana product itself is now characterized by increased potency and varying forms of administration, including food products. These shifts have placed renewed emphasis on the possible harms and medical value of marijuana. This book provides a summary of up-to-date research on marijuana and should serve as a bellwether volume pertaining to prevention, treatment, and policy development regarding this complex drug.

What Is the Evidence of Marijuana as Medicine?

Marijuana as medicine is a controversial and often distorted topic. Medical marijuana in the United States has bypassed the standard process of scientific investigation that is required to determine approval of medicine and has created a political controversy among the American public and in the scientific community. This chapter discusses the science where the heart of the controversy lays—at the question of whether marijuana’s potential benefits outweigh its potential harms. We review the history of marijuana’s development as a medicine and summarize the impacts of medical marijuana laws in the United States and the challenges associated with doing so. We conclude that some benefits of marijuana’s core elements—tetrahydrocannabinol and cannabidiol—are supported by a handful of controlled clinical trials for a very limited number of health problems.

Impact of Marijuana Smoking on Lung Health

This chapter reviews the literature pertaining to the concern that regular smoking of marijuana contributes to the well-known respiratory consequences of regular tobacco smoking, including, chronic obstructive pulmonary disease (COPD) and respiratory cancer. Whereas regular marijuana smoking is associated with symptoms of acute and chronic bronchitis and evidence of microscopic injury to the cells lining the central airways, the majority of community- or population-based studies in regular smokers of marijuana have not found evidence of clinically significant impairment in lung function in comparison with nonsmokers that would be consistent with COPD. However, very few studies have been conducted in older marijuana smokers in the age range when COPD is generally diagnosed, and few longitudinal studies of change in lung function over time have been carried out in smokers of marijuana. Therefore, firm conclusions regarding the potential risks of marijuana for the development of COPD must await additional studies.

Effects of Adolescent Cannabis Use on Brain Structure and Function

The nature, severity, and persistence of effects of cannabis use on the structure and function of the developing adolescent brain is an active area of research. This chapter will review what is known about these relationships during adolescence (i.e., the time between initiation of sexual maturation and completion of higher-order cognitive development; i.e., ages 10–24). In general, the authors find that cannabis has a negative association with neurocognition beyond acute intoxication and that earlier age of onset of regular cannabis use is associated with worse neurocognitive outcomes. The discussion highlights critical relationships between cannabis and brain development, and underlines areas that are incompletely understood and should be further studied to be adequately informed for this era of rapid policy change regarding cannabis regulation.

Recent Epidemiological Trends in Marijuana Use

This chapter provides a description of recent epidemiologic trends in marijuana use among U.S. adolescents and adults. Data from large national surveys conducted in the United States on rates of marijuana use have documented various trends in marijuana use. Specifically, the chapter discusses results from the National Survey on Drug Use and Health, Monitoring the Future, Youth Risk Behavior Surveillance System, and the National Monitoring of Adolescent Prescription Stimulant Study. These surveys show that the prevalence of marijuana use has increased for some subgroups in recent years, but rates of cannabis abuse or dependence among adolescents and adults examined have remained relatively steady.