A new study shows how cannabis-derived CBD can improve schizophrenia-like symptoms in rats.
The symptoms of schizophrenia are wide-ranging and varied. They include so-called positive symptoms - that is, symptoms that do not appear in healthy individuals - negative symptoms, called negative because they are a disruption to normal behavior, and finally, cognitive symptoms.
The latter category includes difficulty paying attention or concentrating, trouble making decisions, as well as problems with comprehending and using new information.
While currently available medication effectively treats positive symptoms - such as hallucinations and delusions - it is less effective in treating cognitive symptoms and negative symptoms, such as reduced speaking, reduced social interaction, and blunted feelings.
Furthermore, antipsychotics can cause a wide range of side effects, including muscle spasms, restlessness, tremors, as well as drowsiness, or dizziness. Some less commonly prescribed medication can lead to weight gain, metabolic changes, an increased risk of diabetes, and high cholesterol.
This is why new research looks at the potential of a cannabis compound called cannabidiol (CBD) for treating the more challenging symptoms of schizophrenia.
The new study - published in the journal Nature - was carried out by a team of researchers from the Illawarra Health and Medical Research Institute (IHMRI) in New South Wales, Australia.
Uncovering the therapeutic potential of CBD
CBD can affect learning, memory, and attention, which suggests that the compound could help manage cognitive symptoms more effectively and with fewer side effects than widely available medication.
The researchers - led by Dr. Katrina Green from the University of Wollongong, Australia - first discovered the therapeutic value of CBD when they previously conducted a review of 27 studies.
"From this review, we found that CBD will not improve learning and memory in healthy brains, but may improve aspects of learning and memory in illnesses associated with cognitive impairment, including Alzheimer's disease, as well as neurological and neuro-inflammatory disorders," explains Dr. Green.
"Evidence suggests that CBD is neuroprotective and can reduce cognitive impairment associated with use of delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis," Dr. Green adds.
Based on this evidence, Ph.D. candidate Ashleigh Osborne, together with Dr. Green - who is her supervisor - set out to examine if CBD can reduce cognitive impairment in rodents.
CBD improved cognition and social interaction in rats
The team - made up of Osborne, Dr. Green, senior professor Xu-Feng Huang, and Ph.D. candidate Ilijana Babic - used a prenatal infection model to investigate the effect of chronic CBD treatment on cognition and social interaction.
First, they infected the pregnant rats in the 15th day of gestation with polyinosinic-polycytidilic acid - a compound commonly used to generate psychiatric disorders such as schizophrenia and autism in rats.
Then, they injected the male rats offspring with 10 milligrams per kilogram of CBD for 3 weeks.
Dr. Green and her team measured the body weight, food, and water intake of the offspring every week.
They tested the rats' cognition and working memory using rewarded alternation in T-maze tests and the Novel Object Recognition test. Additionally, they tested sociability using a social interaction test.
"We found that CBD was able to restore recognition and working memory, as well as social behavior to normal levels. These findings are interesting because they suggest that CBD may be able to treat some of the symptoms of schizophrenia that are seemingly resistant to existing medications. In addition, CBD treatment did not alter body weight or food intake, which are common side effects of antipsychotic drug treatment."
First author Ashleigh Osborne
The researchers caution against the use of cannabis and cannabis-derived products for the treatment of schizophrenia, as the THC in cannabis may worsen schizophrenia symptoms.
Although the results were encouraging, the scientists note that further testing is required to see if CBD has the same therapeutic effect in people.
Next, the team plans to investigate the neurotransmitter signals in the brain to better understand this therapeutic effect.