Saturday, June 7, 2008

Study – Long Term Marijuana use Toxic to the Brain

Recent studies show that marijuana may cause psychosis, increase the risk of heart disease, and provoke heart attack. Researchers now tell us that marijuana may be toxic to the brain, especially the left hippocampus. The hippocampus is responsible for short-term memory, spatial navigation, and the left hippocampus plays a large role in language dominance. The study is published online in the June issue of Archives of General Psychiatry, led by Murat YĆ¼cel, PhD

Changes in the brain were seen by way of MRI in fifteen heavy marijuana users. All were found to have reductions in hippocampal volume. The participants were male, smoked for more than 10 years without using other drugs, and reportedly smoked more than five joints daily. The study is reportedly the first to measure the long-term effects of marijuana on humans. It’s not completely understood whether the change in brain volume comes from loss of neurons, which make up half of the central nervous system, or glial cells, which comprise the other half. Other possibilities include smaller cells, or alternatively, decreased synapse density - tiny cells that transmit information across neurons. Additionally, "the left hippocampus may be particularly vulnerable to the effects of cannabis exposure and may be more closely related to the emergence of psychotic symptoms”.

Another finding included a 7.1% reduction of the smoker’s amygdala, the portion of the brain that lies close to the hippocampus and affects emotions, arousal, hormonal secretions and fear response.

Further research is planned to measure “the degree and mechanisms of long term cannabis-related harm and the time course of neuronal recovery after abstinence."


Analysis Links Low Level Air Pollution to Stroke

Short-term exposure to low level air pollution may increase our risk of stroke, according to data compiled from Neuces County, Texas, home of several oil refineries. Researchers found a 3% increase in strokes and TIA (mini-stroke) the day of, and the day following exposure to fine particulate matter. The report is the first to reveal scientific evidence that air pollution might be related to stroke. Past studies show that air pollution is associated with increased risk for heart disease.

Scientists used information from the Brain Attack Surveillance in Corpus Christi (BASIC) database, a study that compiles information about stroke variances in ethnic populations. Lead investigator, Lynda Lisabeth, PhD, from the University Of Michigan School Of Public Health, in Ann Arbor, reports, "In this particular community, we found there was an association between both acute and short-term exposure to fine particulate matter and stroke and TIA risk. We looked at counts of stroke and TIAs on given days and correlated that with the amount of air pollution on that day.”

Incidence of strokes that occurred between 2001 and 2005 were identified and paired with information from the Texas Commission on Environmental Quality's monitoring operations database. A centrally used monitor, positioned upwind of the oil refineries, was used to find information on fine particulate matter and ozone. Surprisingly, pollution levels were low, leading to concerns about the population at large, many of whom breathe even worse air.

Follow up plans include trying to measure the impact on those with existing lung disease, congestive heart failure, and other subgroups as well as other demographic areas.

Researchers aren’t sure exactly what happens with air pollution to increase the risk of stroke, but Dr. Lisabeth suggests strokes might occur as the result of acute vasoconstriction, or strangulation of blood flow to the brain, and increased blood viscosity. Vasocontstriction is also a common cause of heart attacks. It will be interesting to see further research. We can hope that as studies pile up current air quality standards will be further addressed.