Marijuana use was associated with better performance on measures of sustained attention and inhibitory control among people with bipolar disorder, according to a new study published in the journal Neuropsychopharmacology and funded in part by the National Institute on Drug Abuse and the National Institute of Mental Health.
For the study, researchers from the University of California San Diego and VA San Diego Healthcare System conducted two studies examining how marijuana use and THC affect cognitive functions that are often impaired in people with bipolar disorder, including attention, inhibitory control and the perception of time.
In the first study, researchers compared people with bipolar disorder who used marijuana with those who did not, as well as healthy adults without bipolar disorder. Participants completed a Temporal Discrimination Task, which measures the ability to accurately distinguish lengths of time, and a 5-Choice Continuous Performance Task designed to assess sustained attention and inhibitory control.
People with bipolar disorder who did not use marijuana showed significantly less precise timing than the other groups. In contrast, participants with bipolar disorder who used marijuana performed comparably to healthy nonusers on the timing task.
A similar pattern emerged for sustained attention and inhibitory control. Marijuana users with bipolar disorder performed comparably to healthy participants without bipolar disorder, while bipolar participants who did not use marijuana did not.
The researchers also found that moderate, but not heavy, marijuana use was modestly associated with improved sustained attention among people with bipolar disorder. Those reporting moderate use also showed interval-timing performance similar to that of healthy participants who did not use marijuana.
The research included a separate randomized clinical trial examining acute delta-9 THC administration among people with bipolar disorder who were not regular marijuana users and healthy comparison participants. In that experiment, THC appeared to normalize a difference in time perception observed among participants with bipolar disorder, with those receiving THC showing timing performance comparable to healthy controls.
The researchers note that marijuana use is common among people with bipolar disorder and may in some cases represent an effort to manage symptoms such as racing thoughts and difficulty concentrating.
The authors said the findings warrant additional research into whether cannabinoid-based treatments could be developed to address cognitive deficits associated with bipolar disorder.
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