Cannabis has been shown to cause brain damage in heavy users.New research has proven that heavy sustained cannabis use can damage the brains memory and learning capacity.
The Australian scientists that published the work were able to show that the earlier you start using cannabis and the longer you take it, the greater the negative effect.
"Our results suggest that long-term cannabis use is hazardous to white matter in the developing brain. This was especially true for those who had started in adolescence, as we know the brain is still developing during this time," Lead researcher Dr. Marc Seal, from Melbourne’s Murdoch Children's Research Institute said.
White matter makes up the pathways in the brain. Without it, grey matter cannot communicate, leaving the different parts of the brain unable to share information.
In the study, researchers examined 59 people who had been using cannabis for an average of 15 years. These peoples brain scans were compared to the brain scans of 33 normal non-cannabis using individuals.
The researchers found that long term heavy cannabis use disrupted white matter fibres. This resulted in an 80% reduction in the white matter of users.
The research also showed that the average age people started using cannabis was 16. This is a very worrying statistic because younger peoples brains have not finished forming and so the introduction of cannabis can cause severe damage.
"This is the first study to demonstrate the age at which regular cannabis use begins is a key factor in determining the severity of the brain damage," Seal said.
He and the other researchers found that cannabis use interfered with naturally occurring cannabinoid receptors in the brain. When a young person uses cannabis, these receptors fail to mature. In essence, this stunts the growth of white matter in the brain of younger users.
The most damage seems to be done to white matter in the hippocampus and commissural fibres. This means long term use could also cause problems with learning and concentration.
"These people can have trouble learning new things and they are going to have trouble remembering things," Seal said.
He added that, currently, there is no way of knowing if this damage is reversible. This is very worrying as the brain damage caused by cannabis can be quite severe.
The researchers from Melbourne University said that while more study is needed, they are convinced that the damage from their study was caused by heavy cannabis use and not recreational drug or alcohol usage.
They plan to monitor study participants for a further two years to see if there are any further changes in white matter.