Cannabis, bipolar disorder and Cannabis do not mix well. Consuming cannabis may lead to increased manic and psychotic symptoms and a higher risk of suicide. Can the allure of cannabis really be explained as a form of substance misuse? Why is marijuana so appealing to people with bipolar disorder? Could they be getting any benefit from it?
Alannah Hamilton, University of California, San Diego is a postdoctoral scholar who works with U.C.S.D. These questions were explored by William Perry, a psychiatrist, and Arpi Minassian, a psychiatry professor. Miranda presented her and her colleagues’ unpublished work at this year’s giant Society for Neuroscience conference, which attracted more than 24,000 people earlier this month. She talked to Scientific American about what she discovered in this continuing study, which has been funded by the National Institute on Drug Abuse.
[ An edited transcript of the interview is available . ]
Tell me about your studies.
I’m studying the effects of cannabis on cognition among people with bipolar disorder. Bipolar disorder sufferers report that cannabis is helping to relieve some of their symptoms, including memory, attention, focus, anxiety, and attention.
What did the preliminary study you presented at this conference reveal?
Our study included four comparison groups: healthy participants who did not use cannabis, healthy participants who used cannabis, bipolar disorder patients who did use cannabis, and people with bipolar disorder who use cannabis.
We tested their goal-directed behavior, including risky decisions-making and what we call “effortful motivation”, which is their willingness to continue a task even though the reward potential for them decreases over time. We found that bipolar patients who use cannabis make fewer risky choices and are less likely to take on trivial tasks for too long. Those without bipolar disorder who ingested cannabis had higher levels of risk-taking and more effortful motivation.
How many people participated in the study?
There have been about 60 total participants so far. The study is continuing, and we’re aiming for about 100 in total. We’ll complete it in less than one year.
Previous studies have shown that cannabis can affect bipolar disorder sufferers. What is the difference between your study and others?
A lot of attention in cannabis use for bipolar disorder has traditionally been on whether the drug affects mood symptoms of the disorder, possibly making mania and psychosis more severe . Impaired cognition, such as decision-making, is often overlooked. We’ll be looking at cognitive functions that have a real impact on people’s daily functioning.
Are you also interested in animal studies?
Yes. I have been working with Jared Young at U.C.S.D. His animal work. Our study is different from many other studies on bipolar and cannabis. We are not only looking at it in humans, but also in animals. While the paradigm is to test cognitive functions in humans and mice, we also have very similar tasks in mice. We can also do genetic manipulations in mice and administer certain levels of drugs to animals that we cannot do in humans. We can examine the mechanisms of bipolar disorder, as we believe they exist. For example, dysregulation of the signaling molecule Dopamine. It is much more difficult to examine specific proteins in humans, but that’s what we can do in animal research.
Does anyone have any hypotheses about cannabis and how it might affect the brain?
We believe that cannabis may have an impact on the reward and motivation processing system. Dopamine is responsible for controlling our behavior and the functions we use to achieve certain goals. Bipolar disorder patients might have too high levels of chemical dopamine activity, which could lead to cognitive impairment .
We believe that cannabis may be helping to reduce the amount of dopamine in bipolar disorder patients, which can lead to cognitive impairment.
Could your talk about the implications of your work for possible treatments?
Clinically there would be a concern about cannabis making bipolar disorder’s mania and psychotic symptoms worse. I wouldn’t say that people with bipolar disorder should not use cannabis. Our research could help us understand the mechanisms of cannabis’ effects, which could lead to drug treatments.
What about your work moving forward?
Right now, with our ongoing study, we’re looking at acute effects of THC (tetrahydrocannabinol) versus CBD (cannabidiol). This is probably the most promising direction we are taking in our research. We want to understand the differences between THC and CBD. We want to maximize the therapeutic benefits of cannabis and minimize any harmful side effects. CBD doesn’t have the same psychoactive effects as THC, so it’s not like THC. There is a possibility that CBD could be a better choice for a treatment, but very little data has been collected.
And we’re expanding this to other populations too. This includes HIV patients who suffer from similar neurocognitive impairments. We also plan to study the effects cannabis has on older people, who are also at high risk of cognitive decline. As cannabis legalization increases, more people are turning to it as a medical treatment. However, we don’t know much about the effects of cannabis on the brain. This branch of research is important to me.