CAMH study’s findings may point to a new approach to benefit the high proportion of people with schizophrenia who also have a cannabis use disorder
TORONTO, June 29, 2017 – A new CAMH study suggests that quitting cannabis substantially improved an important aspect of cognition in people with schizophrenia who were chronic cannabis users. Published in April 2017 in Neuropsychopharmacology, it’s the first study to investigate how abstaining from cannabis use for one month impacts cognition or thinking processes in this population.
About one in every 100 people has schizophrenia, a complex and severe mental illness. People with schizophrenia may experience impairments in cognition that profoundly affect everyday living, says Dr. Tony George, senior author of the study and Chief of CAMH’s Addiction Division. Cognition refers to the thinking processes involved in learning, memory and applying knowledge.
High rates of cannabis use among people with schizophrenia and poor outcomes related to its use interested the research team in studying how cannabis abstinence alters cognition, says Dr. George. While about three per cent of the general population has a cannabis use disorder, the rate soars dramatically in people with schizophrenia – it’s estimated that about 25 per cent of people with schizophrenia also have a cannabis use disorder.
The preliminary study, led by Dr. Rachel Rabin while completing her Ph.D. studies, looked at how quitting cannabis use for 28 days affected several areas of cognition, including verbal learning and memory, attention, impulsive behaviours and motor function. A total of 19 people with schizophrenia and a comparison group of 20 people without a mental illness, all of whom had cannabis dependence, attempted to abstain from cannabis use for the full study period. In people with schizophrenia, the area called verbal learning and memory improved significantly – by 40 per cent by the study’s end.
“In people with schizophrenia, our research showed that if you can abstain, you will see better outcomes in a key area of cognition,” says Dr. George, who also heads the Biobehavioural Addictions and Concurrent Disorders Research Laboratory in CAMH’s Campbell Family Mental Health Research Institute, and is Professor of Psychiatry at the University of Toronto.