London study shows differing brain effects of marijuana
By Rachel O'Rourke
A new study by the Institute of Psychiatry at King’s College London, published in January’s edition of Archives of General Psychiatry, has found that class-B drug marijuana has very different effects on people’s behaviour; producing anxiety and paranoia 
in some, and a mellow calm in others.
Although it is still unknown why people react so differently to the drug, the study, which tested fifteen healthy men with minimal previous cannabis use, said that the almost opposing actions of the two key chemicals in marijuana – cannabidiol (CBD) and tetrahydrocannabinol (THC) – hold the answer.
Guinea-pigs in the study were given pills that contained CBD and THC, or a placebo. The participants had computer tasks which measured their reaction times and then underwent brain scans in order to see which brains were more active under the different tasks.
It concluded that men who took THC had faster reaction time to the norm under the circumstances and also reported more delusional thoughts, compared to those on CBD and the placebo.
On the other hand, CBD was shown to have very little effect on participants on its own. Men to take CBD had slower responses to the tasks and, based on previous research, showed that CBD could be used to counteract the effects of THC – suggesting the possible use as an anti-psychotic medication.
The study was spurred in light of research that people who used marijuana increased their chances of suffering from schizophrenia and other mental health problems. The study concluded, in mental health terms, that if marijuana – and specifically THC – conjures altered or abnormal mental states as seen in the study, then delusional and paranoid thinking would ensue.
The synthetic form of marijuana known as K2 – akin to THC, but not CBD - was also mentioned as having harmful effects to mental health, resulting in hallucination and agitation.
The study is expected to be a new source of debate among the medical community as well as upholding the argument against the legalisation of the drug.
According to the Royal College of Psychiatrists, two million people in the UK smoke cannabis and half of all 16 to 19 year olds have tried it at least once. The association said: “In spite of government warnings about health risks, many people see it as a harmless substance that helps you to relax and ‘chill’ – a drug that, unlike alcohol and cigarettes, might even be good for your physical and mental health.
“On the other hand, recent research has suggested that it can be a major cause of psychotic illnesses in those who are genetically vulnerable".
