The immediate desired effects from consuming cannabis include relaxation and euphoria (the "high" or "stoned" feeling), a general alteration of conscious perception, increased awareness of sensation, increased libido and distortions in the perception of time and space.
At higher doses, effects can include altered body image, auditory and/or visual illusions, pseudohallucinations and ataxia from selective impairment of polysynaptic reflexes.
The earliest known reports regarding the sacred status of cannabis in India and Nepal come from the Atharva Veda estimated to have been written sometime around 2000–1400 BCE.
Addiction experts in psychiatry, chemistry, pharmacology, forensic science, epidemiology, and the police and legal services engaged in delphic analysis regarding 20 popular recreational drugs.
Most of the illicit drug emergency room visits involved multiple drugs.
Heavy, long term exposure to marijuana may have biologically-based physical, mental, behavioral and social health consequences and may be "associated with diseases of the liver (particularly with co-existing hepatitis C), lungs, heart, and vasculature".
Because 97% of case-reports also smoked tobacco, a formal association with cannabis could not be made.
Cannabis is believed to be an aggravating factor in rare cases of arteritis, a serious condition that in some cases leads to amputation.A 2012 meta-analysis found that the effects of cannabis use on neurocognitive functions were "limited to the first 25 days of abstinence" and that there was no evidence that such use had long-lasting effects, Compared to non-smokers, people who smoked cannabis regularly in adolescence exhibit reduced connectivity in specific brain regions associated with memory, learning, alertness, and executive function.A study has suggested that sustained heavy, daily, adolescent onset cannabis use over decades is associated with a decline in IQ by age 38.Cannabis was ranked 11th in dependence, 17th in physical harm, and 10th in social harm.According to the United States Department of Health and Human Services, there were 455,000 emergency room visits associated with cannabis use in 2011.
These statistics include visits in which the patient was treated for a condition induced by or related to recent cannabis use.