Marijuana use heightens fearful experiences


Signals transmitted through the brain’s cannabinoid system, a series of receptors influenced by drugs like marijuana, can directly control the prominence of our emotional experiences and memory. Myles Gough reports.


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SYDNEY: Signals transmitted through the brain’s cannabinoid system, a series of receptors influenced by drugs like marijuana, can directly control the prominence of our emotional experiences and memory, a new study suggests.

By understanding how cannabinoid receptors can be manipulated to control the way emotional experiences are processed in the brain, researchers hope to learn more about mental illnesses such as schizophrenia and post-traumatic stress disorder (PTSD).

“People with schizophrenia have great difficulty in accurately perceiving the emotional meaning of incoming sensory information to the brain,” said lead author Steven Laviolette, a neuroscientist at the University of Western Ontario in Canada.

“Our findings reveal a novel circuit in the brain responsible for how drugs like marijuana may modulate emotional experience and memory.”

Leads to heightened emotional memory

The heightened emotional experiences identified by researchers depend on a critical link between the amygdala – a region of the brain associated with fear and memory – and the brain’s prefrontal cortex, which plays a role in rational thought and decision-making.

“We know there are abnormalities in both the amygdala and prefrontal cortex in patients who have schizophrenia, and we now know these same brain areas are critical to the effects of marijuana and other cannabinoid drugs on emotional processing,” said Laviolette.

The study, published in The Journal of Neuroscience, examined the effects of cannabinoid drugs on the brains of rats. Using fear conditioning, impaired rats were presented with a particular scent and then given an electric shock to create an emotional experience.

Blocking receptors may help treat disorders

While activated receptors in the amygdala resulted in heightened emotional experiences, researchers also discovered that these same receptors could be blocked to prevent the formation of emotional memories.

“One implication from our study is that drugs which inhibit these cannabinoid receptors may reverse emotional processing and memory disturbances that are found in neuropsychiatric conditions like schizophrenia and PTSD,” said Laviolette.

Pharmaceutical drugs capable of blocking this pathway could reduce the frequency of psychotic episodes in schizophrenics and could aid people suffering from PTSD who have difficulty coping with the resurgence of traumatic memories.

Blocked but not forgotten

While blocking these receptors can prevent the acquisition of emotional memories, researchers say it has no effect on the ability to recall or consolidate those memories.

David Castle, chair of psychiatry at St. Vincent’s Hospital in Melbourne, said this is one of the more interesting points of the study in terms of helping people with PTSD.

“People within fear situations perceive that fear in a very catastrophic manner, but if you could actually block that fear from the outset without hindering the consolidation of memory this could be a good development,” he said.

An unexplored area

He said it is important not to obliterate these experiences altogether because varying degrees of trauma happen to everyone and learning to cope with these experiences is a part of human development.

“The cannabinoid system is so rich and diverse within the brain and can influence things ranging from memory and emotions, to perception of time and appetite,” said Castle.

“It’s a rather unexplored area in terms of its potential benefits and applications to mental illness.”

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