Marijuana Use Leads to Temporary Cognitive Lapse

Those who seek to legalize marijuana often cite its ability to relieve pain as a reason to make the drug available. For those who have a chronic, painful condition such as cancer or HIV, say advocates, the drug can improve quality of life.

However, there have been multiple studies that have connected instances of psychosis with a history of marijuana use, and the impact of the drug on various situations, such as its role in vehicular accidents, are not fully known.

A recent study broadens the information known about the effects of marijuana, or cannabis, on the brain. The study was conducted by Norwegian researchers and shows that cannabis use leads to a temporary cognitive lapse in individuals who are not psychotic. The results indicate that the effect may develop into long-term psychosis.

The researchers found that there was a difference in brain activity patterns when schizophrenia patients with a history of cannabis use were compared to schizophrenia patients with no history of cannabis use.

The findings support the researchers’ theory that schizophrenics who use marijuana may have a higher level of cognitive ability when compared with schizophrenics with not history of marijuana use. The difference, say researchers, may lie in a difference in susceptibility to psychosis.

The brain activity was similar between the two groups, but there were subtle differences. Lead author Else-Marie Loeberg Ph.D., from the University of Bergen, explained that the differences indicate that the cognitive weakness that indicates the developing schizophrenia is imitated in non-psychotic individuals through the effects of the cannabis.

The results were obtained through the scanning of 26 individuals using fMRI machines as they completed challenging cognitive exercises. During the scan, the patients were told to listen for syllables in each ear and then say which syllable was heard in which ear.

While the task is challenging, the difficulties are especially steep for schizophrenia patients, whose symptoms include difficulty in processing verbal cues, impaired attention levels and lower levels of executive functioning.

The scans revealed that the schizophrenia patients who had a history of cannabis use consistently scored higher on the cognitive tasks, in addition to more correct answers when compared with patients who had schizophrenia and no cannabis use.

The findings are consistent with previous research that show marijuana users with schizophrenic tendencies do not seem to exhibit the neurocognitive weaknesses that are normally present among those diagnosed with schizophrenia.

The findings may suggest that when an otherwise non-psychotic individual initiates cannabis use, there may be an increased risk for the development of schizophrenia.

The findings of the study are published in a recent issue of the journal Frontiers in Psychiatry.