Cannabis has psychoactive and physiological effects when consumed. 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. In some cases, cannabis can lead to dissociative states such as depersonalization and derealization.
Depersonalization is the third most common psychological symptom, after feelings of anxiety and feelings of depression. Depersonalization is a symptom of anxiety disorders, such as panic disorder. It can also accompany sleep deprivation (often occurring when suffering from jet lag), migraine, epilepsy (especially temporal lobe epilepsy), obsessive-compulsive disorder, stress, anxiety, and some cases of low latent inhibition. Interoceptive exposure is a non-pharmacological method that can be used to induce depersonalization.
Drealization can be described as an immaterial substance that separates a person from the outside world, such as a sensory fog, pane of glass, or veil. Individuals may report that what they see lacks vividness and emotional coloring. Emotional response to visual recognition of loved ones may be significantly reduced. Feelings of déjà vu or jamais vu are common. Familiar places may look alien, bizarre, and surreal. One may not even be sure whether what he or she perceives is in fact reality or not. The world as perceived by the individual may feel like it is going through a dolly zoom effect. Such perceptual abnormalities may also extend to the senses of hearing, taste, and smell. The degree of familiarity one has with their surroundings is among one’s sensory and psychological identity, memory foundation and history when experiencing a place. When a person is in a state of derealization, they block this identifying foundation from recall. This “blocking effect” creates a discrepancy of correlation between one’s perception of one’s surroundings during a derealization episode, and what that same individual would perceive in the absence of a derealization episode.
Some immediate undesired side effects include a decrease in short-term memory, dry mouth, impaired motor skills and reddening of the eyes. Aside from a subjective change in perception and mood, the most common short-term physical and neurological effects include increased heart rate, increased appetite and consumption of food, lowered blood pressure, impairment of short-term and working memory, psychomotor coordination, and concentration. Some users may experience an episode of acute psychosis, which usually abates after six hours, but in rare instances, heavy users may find the symptoms continuing for many days. A reduced quality of life is associated with heavy cannabis use.
Cannabis use is associated with neuroanatomic alterations in brain regions rich in cannabinoid receptors, such as the hippocampus, prefrontal cortex, amygdala, and cerebellum. The same review found that greater dose of marijuana and earlier age at onset of use were also associated with such alterations. It is unclear, however, whether these alterations are caused by marijuana use or were present before such use.
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. 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. Cannabis users appear to have smaller hippocampi than nonusers; this finding is based on a series of small studies with inconsistent designs, so it is uncertain. A 2016 meta-analysis found that regular cannabis users tended to have cue reactivity, the intensity of which ranged from moderate to very high.
Cue reactivity is a type of learned response which is observed in individuals with an addiction and involves significant physiological and subjective reactions to presentations of drug-related stimuli (i.e., drug cues). In investigations of these reactions in drug addicts, changes in self-reported drug craving, physiological responses, and drug use are monitored as they are exposed to drug-related cues (e.g., cigarettes, bottles of alcohol, drug paraphernalia) or drug-neutral cues (e.g., pencils, glasses of water, a set of car keys).
Effects of chronic use may include bronchitis, a cannabis dependence syndrome, and subtle impairments of attention and memory. These deficits persist while chronically intoxicated.
Marijuana is the most common illegal drug reported in motor vehicle accidents.
About 9% of those who experiment with marijuana eventually become dependent. The rate goes up to 1 in 6 among those who begin use as adolescents, and one-quarter to one-half of those who use it daily according to a NIDA review. A 2013 review estimates daily use is associated with a 10-20% rate of dependence.
The highest risk of cannabis dependence is found in those with a history of poor academic achievement, deviant behavior in childhood and adolescence, rebelliousness, poor parental relationships, or a parental history of drug and alcohol problems
Acute effects may include anxiety and panic, impaired attention, and memory (while intoxicated), an increased risk of psychotic symptoms, and possibly an increased risk of accidents if a person drives a motor vehicle while intoxicated. Short-term cannabis intoxication can hinder the mental processes of organizing and collecting thoughts. This condition is known as temporal disintegration. Psychotic episodes are well-documented and typically resolve within minutes or hours. There have been few reports of symptoms lasting longer. Studies have found that cannabis use during adolescence is associated with impairments in memory that persist beyond short-term intoxication.
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Cannabis and temporal disintegration in experienced and naive subjects. Casswell S, Marks DF. The effects of 3.3 and 6.6 milligrams of Delta(9)-tetrahydrocannabinol and of placebo on performance of three cognitive tasks were compared for naive subjects and experienced cannabis smokers.
High oral doses of marihuana extract, calibrated for content of 1 (—)-Δ1-tetrahydrocannabinol, significantly impaired the serial coordination of cognitive operations during a task that required sequential adjustments in reaching a goal.
8 normal subjects were given at random either a placebo or extracts of tetrahydrocannabinol. They were tested for impaired immediate memory, speech disorders and temporal disorganization of thinking.
Frontotemporal Dementia (FTD) Frontotemporal dementia (FTD) or frontotemporal degenerations refers to a group of disorders caused by progressive nerve cell loss in the brain's frontal lobes (the areas behind your forehead) or its temporal lobes (the regions behind your ears).