Dr David Potter and GW Pharmaceuticals – a company that is exploring how cannabis could help treat a range of illnesses ranging from epilepsy to cancer – have turned their attention to developing a cannabis-based treatment for psychosis and related illnesses such as schizophrenia. For a drug that is widely seen as a trigger for acute psychotic illness in young users, this at first sounds preposterous. But, as Potter explains, the cannabis plant is much more than just a psychedelic weed. A cannabinoid known as CBD (or cannabidiol) appears to have almost the exact opposite effect.
That cannabis and schizophrenia are linked is widely accepted. Several studies suggest the drug can set off short-term psychotic episodes in those already suffering from the condition. Other research, though, does more than this. It shows that people with schizophrenia are twice as likely as others to use cannabis. This leads some to argue that the drug is actually a cause of schizophrenia rather than just a trigger—a line of evidence sometimes employed by those who wish to keep it illegal.
The relentless crackdown by security forces on the mainly cannabis-smoking youth in Beirut has had several negative repercussions on the Lebanese society. Young, impressionable teenagers in Beirut are increasingly getting drawn to what is called "synthetic cannabis" or otherwise known as "K2" or "spice." A mixture of herbs is usually laced with cannabinoids such as cannabicyclohexanol. The exact effects of this mixture are still not well understood, but early studies suggest a severe increase in chances of psychosis.
New research from Harvard Medical School, in a comparison between families with a history of schizophrenia and those without, finds little support for marijuana use as a cause of schizophrenia. “The results of the current study suggest that having an increased familial morbid risk for schizophrenia may be the underlying basis for schizophrenia in cannabis users and not cannabis use by itself,” note the researchers.
Experts at the Institute of Psychiatry in London are publishing research suggesting that smoking cigarettes may be a contributory cause of schizophrenia (a psychotic disorder). These new findings raise a question - could the most obvious fact about cannabis - that it is usually consumed in combination with tobacco - have been neglected in researching the link between cannabis and psychosis?
Cannabis dependence is a disorder primarily experienced by young adults, especially in higher income countries. It has not been shown to increase mortality as opioid and other forms of illicit drug dependence do. Our estimates suggest that cannabis use as a risk factor for schizophrenia is not a major contributor to population-level disease burden.
Cannabis is associated with psychosis (a symptom) and schizophrenia (an illness where this symptom is persistent) in complex, contradictory and mysterious ways. The evidence does demonstrate various links that we all should all be aware of, especially cannabis users and parents. However, the evidence does not support anything like the level of fear propagated in the media.
Thanks in part to the Netherlands' policy of marijuana decriminalization, there are people living in the Dutch city of Utrecht whose addiction to cannabis prevents them from getting effective treatment for mental illness. According to a September 10 statement from Utrecht Mayor Wolfsen, "There is a group of about eighty people with a chronic psychotic disorder who barely respond to their treatment. A possible explanation for this is their severe dependence [on] cannabis."
A compound found in marijuana can treat schizophrenia as effectively as antipsychotic medications, with far fewer side effects, according to a preliminary clinical trial. Unlike the main ingredient in marijuana, THC, which can produce psychotic reactions and may worsen schizophrenia, cannabidiol (CBD) has antipsychotic effects, according to previous research in both animals and humans.
Marijuana has been shown to have both anxiolytic (anti-anxiety) effects and to induce anxiety and psychosis in certain people. In schizophrenics, it can increase symptoms, and in healthy people it can increase the risk of schizophrenia. Now, new study shows that the two active ingredients in pot, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) may have quite opposite effects on the brain – and behavior – and could explain why pot’s effects can be unpredictable.
New research finds that the two main ingredients in marijuana have opposing effects on it. The study examined 15 normal men who had previously smoked cannabis only a few times. Researchers exposed the men to each of the two most psychoactive ingredients in marijuana — delta-9 tetrahydrocannabinol (THC) and cannabidiol (CBD) and compared their effects with those of a placebo while the participants performed a mental task.
No serious commentator doubts that cannabis is potentially damaging to the user. Like tobacco, it is typically smoked and thus shares the potential for lung disease. Like alcohol, it affects reaction times and may raise the risk of road accidents. Cannabis has also been associated with cognitive impairment, deterioration in education performance (van Ours and Williams 2008), and psychotic illness (Arsenault 2004). Moreover, cannabis is often – albeit contentiously – seen as a causal gateway to more serious drug use (Kandel 2002). The question is what to do about it?
Within the last decade the hitherto little known psychoactive substance of khat has emerged as a regional and international issue. In the Horn of Africa khat production has spurred an economic boom, but dramatic increases in consumption have raised public health concerns. Given the complexity of the topic spanning multiple academic disciplines and fields of professional practice, the need for a systematic overview is urgent.
Researchers, research funders and policymakers should give greater voice to the risks and harms associated with particular cannabis policies and to the evaluation of alternative regulatory frameworks. Given the decades of research and experience with cannabis prohibition, it seems reasonable to reorient the cannabis policy debate based on known policy-attributable harms rather than to continue to speculate on questions of causality between cannabis use and mental illnesses such as psychosis, depression, and related disorders, that will not be definitively answered any time soon
For over two decades, cannabis, commonly known as marijuana, has been the most widely used illicit drug by young people in high-income countries, and has recently become popular on a global scale. Epidemiological research during the past 10 years suggests that regular use of cannabis during adolescence and into adulthood can have adverse effects. Epidemiological, clinical, and laboratory studies have established an association between cannabis use and adverse outcomes.
Martin Frisher, Ilana Crome, Orsolina Martino, Peter Croft
27 June 2009
A recent systematic review concluded that cannabis use increases risk of psychotic outcomes independently of confounding and transient intoxication effects. Furthermore, a model of the association between cannabis use and schizophrenia indicated that the incidence and prevalence of schizophrenia would increase from 1990 onwards.