Cannabis sativa has Δ9-tetrahydrocannabinol (Δ9-THC), isolated in the 1960s , as its main psychoactive compound. The concentration of Δ9-THC in the different presentations of cannabis (marijuana, hashish, skunk) is proportional to the intensity of its toxic effects. In cannabis, considered to be the most consumed illicit substance in the world , increased concentrations of Δ9-THC have been reported in recent years [3–5].
At the same time, there has been an increase in the number of patients reporting to specialized services with complaints related to the use of cannabis. A survey in the USA revealed that between 1992 and 1998 the demand for treatment at specialized services has doubled, with the percentage of admissions for the treatment of cannabis-related disorders (23%) approaching the admission rates relative to cocaine (27%) and heroine (23%), considering all drug-related hospitalizations .
The use of cannabis has been associated with several psychological, behavioral, and social problems . Besides the chronic effects of the continued use of cannabis, such as dependence, abstinence, varying degrees of cognitive impairment, and increased risk of respiratory disorders, its acute effects have also been related to significant physical and mental health problems [7, 8], and an increasing number of emergency admissions has been linked to cannabis use [9, 10].
The intoxication by cannabis is associated with subjective symptoms of euphoria, perceptual distortion, continuous giggling, sedation, lethargy, impaired perception of time, difficulties in the performance of complex mental processes, impaired judgment and social withdrawal . In addition, physical signs of conjunctival hyperemia, increased appetite, dry mouth, and tachycardia can develop in the period of approximately two hours after the use of the substance , corresponding to the plasmatic peak of Δ9-THC.
In general, the acute toxicity of cannabinoids is considered to be low. Nevertheless, there are reports of death by brain infarction - especially among teenagers - following the acute use of marijuana [12, 13] as well as of cases of patients with severe sequelae resulting from this complication . Similarly, there are reports of coma in children induced by the accidental intake of cannabis , in addition to cases of cardiac arrhythmia [16–20], acute myocardial infarction , and transitory ischemic attacks . Factors such as increased heart effort, elevated levels of catecholamine and carboxyhemoglobin in the blood, as well as the occurrence of postural hypotension are among the most commonly reported factors of cardiovascular disease associated with intoxication by cannabis .
It is known that cannabis intoxication leads to impaired motor ability, attention, and short-term memory [8, 23]. In accordance with this, many studies have found a higher prevalence of cannabis use among drivers involved in accidents than in the general population .
Currently, there is consistent evidence that people who use cannabis on a regular basis have a higher proportion of acute psychiatric disorders, aggravated by other factors such as personality traits, pre-existing vulnerability, and substance use at an early age . First-time use and the dose of cannabis are among the main factors related to this occurrence .
Panic and anxiety attacks are among the most commonly reported psychiatric symptoms related to cannabis intoxication and are often responsible for the discontinuation of the use of the substance . Acute psychotic episodes related to cannabis intoxication are described in terms of confusion, disorientation, amnesia, depersonalization, delusions, hallucinations, paranoid ideation, psychomotor agitation, labile affect, and hostility . These symptoms are usually gone after a maximum of one week abstinence . In some cases, psychotic episodes secondary to the use of cannabis can persist for a substantial period of time after the acute intoxication and may have some of the features of acute schizophreniform disorders [24, 27, 28]. Further evidence is provided by a systematic review on longitudinal and population-based studies, which showed that cannabis use significantly increases the risk of developing psychotic illnesses in a dose-dependent manner .
There is strong evidence that cannabis use can have major detrimental effects on the course of the illness when patients with a pre-existing psychotic condition continue to use the drug . In addition to worsening the outcome and exacerbating the symptoms, cannabis use by people with psychosis can lead to sudden behavioral disturbances such as increased proneness to violence, criminal activity, suspiciousness, and hallucinations .
Lately, attempts have been made to better understand the neurobiological mechanisms underlying cannabis-related disorders and the functioning of the endogenous cannabinoid system. There is increasing interest for the development of medications capable to reduce the morbidity of these disorders. Because marijuana intoxication is a major public health problem with a growing demand for assistance at emergency departments, the study of possible pharmacological interventions that might help in the management of the acute effects of cannabis use is of great clinical and social relevance.