It was also shown that giving THC or cannabis correlated with increased bloodflow in these areas, and facilitated activation of the anterior cingulate cortex and frontal cortex when participants were presented with assignments demanding use of cognitive capacity.
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 same review found that greater dose of marijuana and earlier age at onset of use were also associated with such alterations.
A 2010 review found resting blood flow to be lower globally and in prefrontal areas of the brain in cannabis users, when compared to non-users.
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.
A 2015 analysis of six studies found little evidence that long-term or regular cannabis smoking was associated with lung cancer risk, though it could not rule out whether an association with heavy smoking exists.
Cannabis is believed to be an aggravating factor in rare cases of arteritis, a serious condition that in some cases leads to amputation.
Because 97% of case-reports also smoked tobacco, a formal association with cannabis could not be made.