Source: Daily Mail

September 22, 2011

By Claire Bates

Cannabis could help ease the symptoms of post-traumatic stress disorder, scientists say – as long as it was administered early enough.

Researchers from Haifa University, in Israel, found that cannabinoids – the active compound in cannabis – blocked feelings of anxiety in rats after they experienced a stressful episode.

However, it was only effective if it was administered in the first 24 hours after the traumatic event.

‘We found that there is a ‘window of opportunity’ during which administering synthetic marijuana helps deal with symptoms simulating PTSD in rats,’ said study leader Dr Irit Akirav.

Rats were used because they have similar physiological reactions to traumatic and stressful events as humans.

Cannabis is a Class B drug in Britain and is illegal to use or sell. Regular use has been linked with an increased risk of developing psychotic illnesses such as schizophrenia.

However, there are a handful of cannabinoid medicines derived from the cannabis plant that have been licensed by the Medicines and Healthcare products Regulatory Agency in the UK.

In the first part of the study, published in the journal Neuropsychopharmacology, the researchers exposed a group of rats to extreme stress.

They observed that the rats displayed symptoms resembling PTSD in humans, such as an enhanced startle reflex and impaired learning.

The rats were then divided into four groups. One was given no cannabis at all; the second was given a cannabis injection two hours after being exposed to a traumatic event; the third group after 24 hours and the fourth group after 48 hours.

A week later, the researchers examined the rats and found that the group that had not been administered marijuana and the group that got the injection 48 hours after experiencing trauma continued to display PTSD symptoms as well as a high level of anxiety.

By contrast, the PTSD symptoms disappeared in the rats that were given cannabis two or 24 hours after experiencing trauma, even though these rats had also developed a high level of anxiety.

‘This indicates that the marijuana did not erase the experience of the trauma, but that it specifically prevented the development of post-trauma symptoms in the rat model,’ said Dr Akirav.

He added that because the human life span is significantly longer than that of rats, one could assume that the window of time when the drug would be effective would be longer for humans.

The second stage of the study sought to understand the brain mechanism that is put into operation during the administering of cannabis.

To do this, they repeated stage one of the experiment, but after the trauma they injected the synthetic cannabinoid directly into the amygdala area of the brain, the area known to be responsible for response to trauma.

The researchers found that the marijuana blocked development of PTSD symptoms in these cases as well.

From this the researchers were able to conclude that the effect of the marijuana is mediated by a CB1 receptor in the amygdala.

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