Cannabis and schizophrenia
The 2nd International Cannabis and Mental Health Conference was recently held in London (May 1-2) and has ignited much controversy about marijuana leading to psychotic symptoms and schizophrenia. But behind all the smoke, the broad claims and scary titles, many of the articles focus on only two studies: D’Souza’s on THC and schizophrenia and McGuire’s MRI scans of the brain. Without going into the details of their experiments, let’s just look at what they claim to have found.
These are the symptoms of schizophrenia discovered by Dr. Deepak Cyril D’Souza:
"Δ-9-THC produced schizophrenia-like positive and negative symptoms, altered perception, increased anxiety, produced euphoria, disrupted immediate and delayed word recall, impaired performance on tests of attention and working memory without impairing orientation."
What this looks like is a list of positive and negative symptoms of getting high. Altered perception can be said of many substances, without it having to be psychotic. Increased anxiety often comes with altered perception, since some people get worried when everything looks unfamiliar. It seems absurd to classify euphoria as a sign of madness. Meanwhile, impairment of attention and working memory comes hand in hand with most intoxicants, including alcohol. The study reports that these symptoms get more severe in people already diagnosed with schizophrenia, but if those are the symptoms being searched for, it seems essentially like saying that schizophrenic people get high too.
The results from Prof. Philip McGuire scans:
"THC attenuated [weakened] activation in the left temporal cortex compared to placebo… THC attenuated activation in the right inferior frontal cortex and its effect in this region predicted the severity of psychotic symptoms induced by THC. THC attenuated activation in the auditory cortex while subjects listened to speech."
Now, it’s well known that weed effects the auditory cortex, that’s why so many musicians smoke and so many smokers like to listen to music while high. The weakened auditory cortex while listening to speech is likely tied to the weakened left temporal cortex, which is responsible for sentence formation. Being high, similar to other types of intoxication, can make it hard to concentrate on long stories and sometimes you forget to finish your, what was I saying? The scan, in this case, backs up what could be easily hypothesized from the symptoms with a rudimentary knowledge of neurology. Meanwhile, the weakened activation of the right inferior frontal cortex, the region associated with face recognition, thus also with the ability to read emotions and acting appropriately in social situations, is just a part of a body of other visual hallucinations/attenuations, the most desired aspect for most users, and is what understandably accounts for the paranoia and general whackiness often experienced by smokers. Linking it with schizophrenia, which only recently has been connected to impaired face recognition, is tentative at best. So, much of the recent press on the matter seems to have blown a few carefully worded findings way out of proportion. Smoking weed does not make you schizophrenic, just because being high is kind of similar to it.
2nd International Cannabis and Mental Health Conference: Programme and Abstract book [pdf]
