The authors cautioned that "evidence is needed, and further research should be considered, to prove causal associations of marijuana with many physical health conditions".Cannabis use disorder is defined in the fifth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as a condition requiring treatment. Several drugs have been investigated in an attempt to ameliorate the symptoms of stopping cannabis use. Such drugs include bupropion, divalproex, nefazodone, lofexidine, and dronabinol. Of these, dronabinol (a trade name for THC) has proven the most effective. The drugs buspirone and rimonabant have shown some success in helping maintain cannabis abstinence.There is evidence that long-term use of cannabis increases the risk of psychosis, regardless of confounding factors, and particularly for people who have genetic risk factors. A 2019 meta-analysis found that 34% of people with cannabis-induced psychosis transitioned to schizophrenia. This was found to be comparatively higher than hallucinogens (26%) and amphetamines (22%).Long-term cannabis users are at risk for developing cannabinoid hyperemesis syndrome (CHS), characterized by recurrent bouts of intense vomiting. The mechanism behind CHS is poorly understood and is contrary to the antiemetic properties of cannabis and cannabinoids. Of those who went to the emergency department (ED) with recurrent vomiting in one institution in the United States from 2005 to 2010, about 6% had the condition. Effects in pregnancy
Cannabis consumption in pregnancy might be associated with restrictions in growth of the fetus, miscarriage, and cognitive deficits in offspring based on animal studies, although there is limited evidence for this in humans at this time.
Oral ingestion use eliminates the need to inhale toxic combustion products created by smoking and therefore negates the risk of respiratory harm associated with cannabis smoking. Effects on driving
While several studies have shown increased risk associated with cannabis use by drivers, other studies have not found increased risk. Cannabis usage has been shown in some studies to have a negative effect on driving ability. The British Medical Journal indicated that "drivers who consume cannabis within three hours of driving are nearly twice as likely to cause a vehicle collision as those who are not under the influence of drugs or alcohol".In Cannabis and driving: a review of the literature and commentary, the United Kingdoms Department for Transport reviewed data on cannabis and driving, finding although impaired, "subjects under cannabis treatment appear to perceive that they are indeed impaired. Where they can compensate, they do". In a review of driving simulator studies, researchers note that "even in those who learn to compensate for a drugs impairing effects, substantial impairment in performance can still be observed under conditions of general task performance (i.e. when no contingencies are present to maintain compensated performance). "A 2012 meta-analysis found that acute cannabis use increased the risk of an automobile crash.