If the link is proved, it could lead to the development of treatments based on the active ingredient of cannabis, tetrahydrocannabinol (THC), without its intoxicating effects.
Researchers have found that regular users of the drug had lower levels of the hormone insulin after fasting – a signal that they are protected against diabetes. They also had reduced insulin resistance. Cannabis is widely smoked in the United States with over 17 million current users of whom more than four million smoke it on a daily basis. In the UK latest figures show 2.3 million people used cannabis in the last year, but the numbers have declined in the last decade.
Two US states have recently legalised its recreational use and 19 others have legalised it for medical purposes by patients with one of several conditions including multiple sclerosis and cancer. THC has already been approved to treat the side effects of chemotherapy, nausea in cancer patients, anorexia associated with AIDS and other conditions.
The study involved almost 5,000 patients who answered a questionnaire about their drug use and were part of the National Health and Nutrition Survey between 2005 and 2010. The results showed almost 2,000 had used cannabis at some point in their lives and more than one in 10 (579) were current users. Only those who had used cannabis within the past month showed evidence of protection against diabetes, suggesting that the effects wear off in time. Current users of the drug had 16 per cent lower fasting insulin than those who had never used the drug.
Murray Mittleman, of the Cardiovascular Epidemiology Research Unit at the Beth Israel Deaconess Medical Centre in Boston, and lead author of the study published in The American Journal of Medicine, said previous studies had shown lower rates of obesity and diabetes in marijuana users.
Two previous surveys had also shown that although cannabis users consume more calories they have a lower body mass index. The mechanisms underlying this paradox are unknown, the authors say. Joseph Alpert, professor of medicine at the University of Arizona College of Medicine, Tucson, and editor in chief of the journal, said: “These are remarkable observations that are supported by basic science experiments that came to similar conclusions.
“We desperately need a great deal more basic and clinical research into the short and long term effects of marijuana in a variety of clinical settings such as cancer diabetes and frailty of the elderly.”
Almost one in 20 adults in the UK has diabetes, of which 2.6 million are diagnosed and 500,000 are undiagnosed. Rates are rising in this country and around the world, driven by Western lifestyles, and the number of cases is expected to exceed 4 million in the UK by 2025. The illness increases the risk of heart failure, kidney failure, and death – and is one of the biggest health challenges facing the UK.
By Jeremy Laurance
A new study has found that participating in an 8-week meditation training program can have measurable effects on how the brain functions even when someone is not actively meditating. In their report in the November issue of Frontiers in Human Neuroscience, investigators at Massachusetts General Hospital (MGH), Boston University (BU), and several other research centers also found differences in those effects based on the specific type of meditation practiced.
“The two different types of meditation training our study participants completed yielded some differences in the response of the amygdala — a part of the brain known for decades to be important for emotion — to images with emotional content,” says Gaëlle Desbordes, PhD, a research fellow at the Athinoula A. Martinos Center for Biomedical Imaging at MGH and at the BU Center for Computational Neuroscience and Neural Technology, corresponding author of the report. “This is the first time that meditation training has been shown to affect emotional processing in the brain outside of a meditative state.”
Several previous studies have supported the hypothesis that meditation training improves practitioners’ emotional regulation. While neuroimaging studies have found that meditation training appeared to decrease activation of the amygdala — a structure at the base of the brain that is known to have a role in processing memory and emotion — those changes were only observed while study participants were meditating. The current study was designed to test the hypothesis that meditation training could also produce a generalized reduction in amygdala response to emotional stimuli, measurable by functional magnetic resonance imaging (fMRI).
Participants had enrolled in a larger investigation into the effects of two forms of meditation, based at Emory University in Atlanta. Healthy adults with no experience meditating participated in 8-week courses in either mindful attention meditation — the most commonly studied form that focuses on developing attention and awareness of breathing, thoughts and emotions — and compassion meditation, a less-studied form that includes methods designed to develop loving kindness and compassion for oneself and for others. A control group participated in an 8-week health education course.
Within three weeks before beginning and three weeks after completing the training, 12 participants from each group traveled to Boston for fMRI brain imaging at the Martinos Center’s state-of-the-art imaging facilities. Brain scans were performed as the volunteers viewed a series of 216 different images — 108 per session — of people in situations with either positive, negative or neutral emotional content. Meditation was not mentioned in pre-imaging instructions to participants, and investigators confirmed afterwards that the volunteers had not meditated while in the scanner. Participants also completed assessments of symptoms of depression and anxiety before and after the training programs.
In the mindful attention group, the after-training brain scans showed a decrease in activation in the right amygdala in response to all images, supporting the hypothesis that meditation can improve emotional stability and response to stress. In the compassion meditation group, right amygdala activity also decreased in response to positive or neutral images. But among those who reported practicing compassion meditation most frequently outside of the training sessions, right amygdala activity tended to increase in response to negative images — all of which depicted some form of human suffering. No significant changes were seen in the control group or in the left amygdala of any study participants.
“We think these two forms of meditation cultivate different aspects of mind,” Desbordes explains. “Since compassion meditation is designed to enhance compassionate feelings, it makes sense that it could increase amygdala response to seeing people suffer. Increased amygdala activation was also correlated with decreased depression scores in the compassion meditation group, which suggests that having more compassion towards others may also be beneficial for oneself. Overall, these results are consistent with the overarching hypothesis that meditation may result in enduring, beneficial changes in brain function, especially in the area of emotional processing.”
Eric Schwartz, PhD, of the BU Department of Electrical and Computer Engineering and Center for Computational Neuroscience and Neural Technology, is senior author of the Frontiers in Human Neuroscience report. Additional co-authors are Lobsang T. Negi, PhD, and Thaddeus Pace, PhD, Emory University; Alan Wallace, PhD, Santa Barbara Institute for Consciousness Studies; and Charles Raison, MD, University of Arizona College of Medicine. The study was supported by grants from the National Center for Complementary and Alternative Medicine, including an American Recovery and Reinvestment Act grant to Boston University.