Marijuana may cause brain inflammation that sets off a genetic time-bomb for schizophrenia in predisposed teenagers – but an anti-inflammatory drug might block the harmful effects a new study suggests.
As marijuana legalization sweeps the US and becomes increasingly popular among (and accessible to) teenagers, health officials are scrambling to understand the risks it comes with.
The link between marijuana and schizophrenia has been studied often, and seems hard to deny though how one affects the other is a muddier question.
But scientists at Johns Hopkins University believe that they have uncovered how marijuana can be the trigger for schizophrenia in teens that are already genetically predisposed to the disorder.
In teenage brains, THC in marijuana may interact with genes involved in schizophrenia to cause inflammation and, in turn, contribute to the onset of the disorder, a new study finds
Studies on marijuana and schizophrenia are a confounding assortment.
Some suggest that those predisposed to the mental health disorder are more likely to like weed.
Others have said it works the other way around.
But the largest body of research suggests that teen marijuana use increases the risks of psychosis in young people.
And the risks of developing schizophrenia increase the more people predisposed to the disorder use it and the earlier they start doing so.
Scientists have long suspected this might have something to do with inflammation but were unsure what.
Now, the Johns Hopkins team has uncovered a likely mechanism.
Previous research has estimated that about 10 genes may be involved in inherited risks for schizophrenia.
Much like diabetes (and most mental illnesses), these genes alone do not necessarily mean someone will develop the disease. Rather, the influence of environmental factors likely interact with and ‘activate’ a genetic predisposition.
To test how marijuana might interact with these genetic risks, the Johns Hopkins team bred mice with an analogue gene that would predispose them to the animal version of schizophrenia.
These mice had a shoddy version of the DISC1 gene, which made them vulnerable to certain kinds of inflammation and brain damage that has been linked to mental illness.
Next, the mice were given injections of THC – the psychoactive compound in weed – that would roughly equate what a teenager who smoked weed on a daily basis would be exposed to.
Then, they gave the mice a break.
‘Essentially, we let them have their fun as teenagers and then let enough time elapse to their young adulthood, or in human terms the time when people reach their late 20s, are living an adult life and may begin to notice cognitive problems,’ explained Dr Mikhail ‘Misha’ Pletnikov, a psychiatry professor at Johns Hopkins.
These mice were compared to control animals that had the faulty gene, but weren’t exposed to THC, and to mice that didn’t have the faulty gene but were exposed to THC.
Down the line, the mice with bad genes and a marijuana habit suffered more inflammation in parts of the related to memory and cognition.
The Johns Hopkins team discovered that for the genetically predisposed mice, THC kicked on 56 inflammation-causing genes which and, they suspected, the inflammation seemed to in turn trigger cognitive and memory trouble in the mice.
To test that theory – and explore a possible preventative measure, the scientists started a new generation of mice with DISC1 mutations on the THC reginmen.
But this time, before each dose of the psychoactive drug, the mice were given an anti-inflammatory drug.
Once those mice were in the equivalent of their 20s, their memory and cognition were tested.
This time, the ice performed just fine. The drug seemed offset any traces of evidences that the mice had been high daily as ‘teenagers.’
‘If our results turn out to be applicable to people, they suggest we could develop safer anti-inflammatory treatments to prevent long-term consequences of marijuana use,’ says Dr Pletnikov.