The Western Cape High Court recently ruled in favour of Dagga eventually being used legally for private use at home. But what effects does Dagga have on the brain?
By Dr Samantha J. Brooks Ph.D.
As a neuroscientist, and with the recent decision by the Western Cape High Court to consider legalising the use of Dagga for private use at home in two years’ time (using Dagga can still currently land you in jail), I advise you to carefully consider the influence it might have on the brain. Some say Dagga causes pleasure and might even be helpful for people with illness and disease. But there is also evidence to suggest that long term use may be related to mental illness and hard-to-reverse negative effects. Considering the effects on the brain might help us to understand whether we should support strict laws to prevent people from using Dagga, or whether we should rather be campaigning to relax those laws. Most of us probably know someone who has tried Dagga, perhaps you have tried it in the past or even currently use it? With all the controversy in mind, what does Dagga really do to the brain? An informed view of the effects of Dagga on the brain is good for personal benefit, as well as for the health of our community in Harfield Village, and for society as a whole. By fully appreciating the effects that Dagga might have on our brains, we can decide for ourselves whether we should use it.
Dagga – the name for Cannabis or marijuana in South Africa - refers to the dried leaves, flowers, stems and seeds of the hemp plant Cannabis sativa. The plant contains a mind-altering, difficult to pronounce chemical – delta-9-tetra-hydro-cannabinol, or THC for short (much easier to say!). THC is the active ingredient that is crumbled down and is popular to smoke in hand-rolled cigarettes (joints), in pipes or water pipes (bongs), emptied cigars (blunts) and vaporisers. THC is regarded as a psychedelic that acts on cannabinoid receptors and the release of dopamine in the brain, producing both short and long term effects on a person’s ability to function normally. While it’s general use in popular culture is often regarded as negative and related to crime and anti-social behaviour, some also argue that it is pleasurable, relaxing and that cannabis-based products, such as Hemp Oil may have positive, anti-inflammatory effects on those with serious illness such as epilepsy, cancer and multiple sclerosis, although this is not yet proven. In fact, the late South African Politician, Mario Oriani-Ambrosini, who sadly died of lung cancer in 2014, campaigned for the medical use of marijuana and suggested that it helped his long battle with terminal, inoperable disease.
What then, are the short and long-term effects of Dagga on the brain, and are they generally positive or negative? Dagga, or cannabis, acts on receptors in the brain that release opioids and dopamine, often leading to euphoric, relaxing effects on behaviour and thought processes. In the short-term, cannabis may slow down thought and reaction speed, alter judgement, impair memory and coordination, blurring or altering vision and bodily sensations, and so it would be dangerous to operate machinery or drive a car under the influence of cannabis. On the longer term however, cannabis may lower stress and tension, but may also lead to cognitive deficits or even more serious mental illness such as anxiety, depression and schizophrenia/psychosis. 
The mixed scientific findings regarding the effects of Dagga on the brain may well be due to genetic susceptibility. In other words, some genes are copied differently and change over generations, a term in science known as a single nucleotide polymorphism (or SNP for short, again, much easier to pronounce!). My colleagues at the Institute of Psychology, Psychiatry and Neuroscience at King’s College in London have done extensive work on this, and have suggested that cognitive impairments, or even psychosis after using cannabis may occur if a person has a certain type of SNP on a gene known as COMT, which is linked to the functioning of the prefrontal cortex. However, as we all know, it is not only genes that play a part in our behaviour, but also the environment, and my colleagues also highlight the very important role of social factors. The bottom line is, if you have genetic susceptibility and experience negative social factors, such as unemployment, poverty and social isolation (few friends and family nearby), and you choose to smoke Dagga, it could have very damaging and long-term effects on the brain. And so these factors together could explain why the Western Cape High Court ruled to consider, but not yet implement, the relaxation of the laws on private use of Dagga at home.
Dr Samantha Brooks is a neuroscientist at the UCT Department of Psychiatry and Mental Health, specialising in the neural correlates of impulse control from eating disorders to addiction. For more information on neuroscience at UCT and to contact Samantha, see www.drsamanthabrooks.com.
