Contemporary uses of cannabis are as a recreational drug, as religious or spiritual rites, or as medicine; the earliest recorded uses date from the 3rd millennium BC.[9] In 2004, the United Nations estimated that global consumption of cannabis indicated that approximately 4% of the adult world population (162 million people) used cannabis annually, and that approximately 0.6% (22.5 million) of people used cannabis daily.[10] In the United States, cannabis is the most commonly used illicit drug; 5.1% of Americans said they used marijuana in the past 30 days. In 1977, 38% of 12th graders reported using cannabis in the past month; in 2011, 23% of the same age group reported using cannabis in the same time span.[11] Since the early 20th century cannabis has been subject to legal restrictions with the possession, use, and sale of cannabis preparations containing psychoactive cannabinoids currently illegal in most countries of the world; the United Nations has said that cannabis is the most-used illicit drug in the world.[12][13]
Effects
Main article: Effects of cannabis

Main short-term physical effects of cannabis
Cannabis has psychoactive and physiological effects when consumed. Some alternative media sources report that minimum amount of THC required to have a perceptible psychoactive effect is about 10 micrograms per kilogram of body weight.[14][medical citation needed] Aside from a subjective change in perception and, most notably, mood, the most common short-term physical and neurological effects include increased heart rate, increased appetite and consumption of food[medical citation needed],[15] lowered blood pressure, impairment of short-term and working memory,[16] psychomotor coordination, and concentration. Long-term effects are less clear.[17][18] In humans, relatively few adverse clinical health effects have been documented from chronic cannabis use.[medical citation needed][19]
Psychoactive classification
Main article: Psychoactive effects
While many psychoactive drugs clearly fall into the category of either stimulant, depressant, or hallucinogen, cannabis exhibits a mix of all properties, perhaps leaning the most towards hallucinogenic or psychedelic properties, though with other effects quite pronounced as well. THC is typically considered the primary active component of the cannabis plant; various scientific studies have suggested that certain other cannabinoids like CBD may also play a significant role in its psychoactive effects.[20][21][22]
Safety
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Cannabis is ranked one of the least harmful drugs by a study published in the UK medical journal, The Lancet.[23]
Cannabis research is challenging since the plant is illegal in most countries.[24][25][26][27][28] There is not enough evidence to reach a conclusion, either way, on the effect of cannabis on overall risk of death or lifespan due to the low number of studies.[29][30] Cannabis is considered to never have led to overdose death[31] though there are medical reports of occasional infarction, stroke and other cardiovascular side effects.[32] Marijuana's cardiovascular effects are not associated with serious health problems for most young, healthy users.[32] According to a 2006 United Kingdom government report, using cannabis is much less dangerous than tobacco, prescription drugs, and alcohol in social harms, physical harm, and addiction.[33]
Dr. Stephen Ross, a professor of child psychiatry and addiction at New York University's Tish Hospital explains reports of cannabis-related deaths: "deaths associated with the drug are the result of activities undertaken while on the drug, such as driving under the influence".[34] The US Substance Abuse and Mental Health Services Administration stated in its July 2001 report from the Drug Abuse Warning Network Mortality Data: "Marijuana is rarely the only drug involved in a drug