Treating Depression With CannabinoidsProhibitionists sometimes claim marijuana causes depression and scoff at marijuana as a treatment for depression. Here a Viennese doctor describes repeated clinical successes using oral THC to treat depression.

Understanding the Association Between Adolescent Marijuana Use and Later Serious Drug Use: Gateway Effect or Developmental Trajectory? This rather complicated study looks at the “gateway theory” through data collected from 510 pairs of twins who participated in a very large, long-term health study — and the gateway theory doesn’t emerge with much backing.

Toxicology of Cannabis and Cannabis ProhibitionThis review describes short and long term negative effects of marijuana use from a cost-benefit perspective.

Testing Hypotheses About the Relationship Between Cannabis Use and Psychosis The relationship between marijuana use and psychosis is a subject of ongoing controversy. In this study, a respected group of Australian researchers took the data on marijuana use rates and rates of schizophrenia and ran a series of computer models to test the possibilities that marijuana: a) causes schizophrenia, b) precipitates schizophrenia in vulnerable persons, c) aggravates schizophrenia in people who already have it, or d) that schizophrenics are more likely to use marijuana (i.e. that marijuana use is the effect, not the cause, of schizophrenia).

Some Go Without a Cigarette This study examined differences between youth who use both tobacco and marijuana compared to youth who use marijuana only, and to youth using neither substance. The marijuana-only adolescents showed better functioning than those who also use tobacco.

A Review of the Published Literature Into Cannabis Withdrawal Symptoms in Human Users We hear regularly from prohibitionists that marijuana is addictive, but some experts consider the evidence unconvincing.

A Preliminary DTI Showing No Brain Structural Change Associated With Adolescent Cannabis UseThe question of whether marijuana causes brain damage, especially among adolescents, remains controversial even though most recent evidence indicates no correlation.

Predictors of Marijuana Use in Adolescents Before and After Licit Drug Use: Examination of the Gateway Hypothesis This prospective, decade-long study finds no support for the “gateway theory” that marijuana causes youth to move on to hard drug use.

Polydrug Use, Cannabis, and Psychosis-Like SymptomsMuch of the purported link between marijuana use and psychosis is based on correlations between marijuana use and schizophrenia-like symptoms or traits, called “schizotypal personality.” But this study suggests that the effects of other drugs also used by some who use marijuana may be confounding such findings.

A Pilot Clinical Study of 9-Tetrahydrocannabinol in Patients With Recurrent Glioblastoma MultiformeTHC and other cannabinoids have been shown to have marked anti-cancer action in laboratory and animal studies. This article describes a clinical pilot study in which THC was injected directly into tumors in terminal brain cancer patients via catheter (tube) to assess feasibility and safety of the procedure.

Neuroscience of Psychoactive Substance Use and Dependence While by no means an anti-prohibitionist document, this World Health Organization report makes a number of interesting points. The report notes, “despite intensive interdiction efforts, there always seems to be enough [drugs] available to users.”

The Neuropsychological Correlates of Cannabis Use in Schizophrenia: Lifetime Abuse/Dependence, Frequency of Use, and Recency of Use – Schizophrenia, a chronic mental illness, is often accompanied by poorer cognitive functioning, and some research has suggested that marijuana may worsen schizophrenia. But this case-control study shows enhanced cognitive functioning in schizophrenic subjects who use marijuana.

Neuropsychiatry: Schizophrenia, Depression and Anxiety Scientific consensus on the role of marijuana in psychological disorders is still lacking, after hundreds of years of speculation and study. Recent evidence of dysregulation of the body’s endocannabinoid system in schizophrenics is beginning to shed new light on some of these questions.

Motives for Cannabis Use as a Moderator Variable of Distress Among Young Adults – A number of studies have found higher rates of various psychiatric problems among marijuana users, and there has been much debate about whether marijuana causes these problems or whether those with psychological issues are simply more likely to use it. In this study, Swiss youth were followed for two years to determine how their motive for marijuana use interacts with levels of psychological distress.

Marijuana Use and the Risk of Lung and Upper Aerodigestive Tract Cancers: Results of a Population-Based Case-Control StudyThis study, co-authored by Donald Tashkin of UCLA, one of the world’s leading experts on the effects of marijuana on the lungs, compared 1,212 cancer patients with 1,040 cancer-free controls matched for age, gender and neighborhood in order to see if there was a relation between marijuana use and cancers of the lungs, throat and mouth (cancers commonly caused by cigarette smoking).

Long-Term Effects of Exposure to Cannabis – Oxford University pharmacologist Leslie Iversen reviews the literature on the effects of long-term marijuana use. Iversen finds that most purported cognitive impairment associated with marijuana dissipates when use ceases.

Human Cannabinoid Pharmocokinetics This review provides in-depth evaluation of marijuana absorption, metabolism and excretion.

Further Consideration of the Classification of Cannabis Under the Misuse of Drugs Act 1971 – In 2005, concerned about reports linking marijuana use to mental illness, the British government asked the Council to take another look at the 2004 “downgrading” of marijuana, which had placed it in the least harmful category of illicit drugs and eliminated most marijuana possession arrests.

Evidence-Based Answers to Cannabis QuestionsThis 60-page report is an evidence-based literature review of marijuana, based only upon research that followed well-accepted research designs, included strong statistical and procedural controls and passed a careful review by independent scientists.

The Evidence Base for the Classification of Drugs – As part of its evaluation of Britain’s system for classifying illicit drugs, Parliament commissioned the European branch of RAND Corporation, one of the world’s most respected think-tanks, to study the evidence underlying the classification of several specific drugs, including marijuana.