Good hit vs bad hit

Western Researchers Discover Potential Key to PTSD in Cannabis

Navaneeth Mohan

For a drug that was consumed by nearly 5 million Canadians in the final quarter of 2018, marijuana has been a curiously under-researched topic. The effects of marijuana on the mammalian brain is poorly understood, especially in humans. 

Consider the diverse reactions of people under the influence of marijuana. For most users, cannabis will induce a euphoric high. Although, some people experience an anxiety ridden ‘bad hit’. Moreover, different strains of cannabis can produce different experiences. 

Until recently, the physiological mechanisms underlying such varying effects were not pinpointed. Now, researchers at Western University’s Laviolette Lab, have determined which region of the brain is primarily responsible for inducing diverse experiences.  

“Translational rodent research performed in our lab has identified highly specific target regions in the brain that seem to independently control the rewarding and addictive properties of marijuana versus the negative psychiatric side-effects associated with its use, ” said Dr. Laviolette in a media release. Dr. Laviolette was referring to the Nucleus Accumbens (NA), which has been known to play a significant role in the cognitive processing of motivation and reward. Steven Laviolette’s lab was also behind the discovery of the brain’s opiate addiction ‘switch’. 

“The NA was traditionally seen as the reward centre of the brain but, a lot more evidence has suggested that it is also responsible for negative feelings”, said Post-Doctoral fellow Dr. Christopher Norris. This study was Dr. Norris’s Ph.D thesis. 

In other words, the NA is the interface between your emotions and your actions. It’s what drives your behaviour towards or away from a particular outcome or object. The influence of psychoactive compounds on this region is being studied in rats at Dr. Steven Laviolette’s lab. 

“There is a sub-region of the NA called the Nucleus Accumbens Shell (NASh), which can be further subdivided into the front and back part of the structure. What we found was that infusion of THC in the front part produces strong positive feelings and infusion of THC in the back part produces strong negative feelings,” said Dr. Norris in an interview with Radio Western. 
The other prominently active compound of cannabis is Cannabidiol (CBD). Dr. Norris’s Ph.D also dealt with the effect of CBD on the NASh. Unlike THC, CBD is not psychoactive but, according to Dr. Norris’ research on rat brains, CBD affects the formation of memories. 

‘We showed that if we infused CBD directly into the NA while the rats were encoding the fear memory, we could block the emotional encoding of the memory. This suggests that CBD can be potentially used to treat or prevent the formation of fearful memory in PTSD or schizophrenia,’ said Dr. Norris. 

While this may be a reason for PTSD patients to turn to cannabis products in an attempt to self-medicate, Dr. Norris advises caution. His study also showed that infusing THC in the posterior part of the NASh can aggravate fearful memories. 

“An interesting statistic collected by the Veteran’s Affairs in United States shows that while every drug of abuse has been decreasing among combat veterans with PTSD, cannabis use has increased dramatically, suggesting that they are self-medicating,” said Dr. Norris.  

It should be noted that Christopher Norris is an active user and vocal proponent of medical marijuana.  “I have a chronic pain condition, Ehler-Danlos-Syndrome. One of the difficulties of treating chronic pain is nothing works very well except dangerous addictive drugs like opioids. I found that medical marijuana could help my pain enough that I could stay off opioids,” said Dr. Norris. 

EDS is a genetic disorder that weakens collagen, a connective and structural protein in our bodies. Patients of EDS suffer from constant injuries, muscle tears, and loose joints. 

Now, armed with his research expertise in reward systems and fueled by his life-long experience with chronic pain, Dr. Norris is a Postdoctoral fellow at the Pittsburgh Centre for Pain. He wants to learn the mechanisms of pain and thus treat pain without using addictive opioids.