Teen cannabis users have poor long-term memory in adulthood

Teens who were heavy marijuana users -- smoking it daily for about three years -- had an abnormally shaped hippocampus and performed poorly on long-term memory tasks, reports a new study. The hippocampus is important to long-term memory, which is the ability to remember life events. The brain abnormalities and memory problems were observed during the individuals' early twenties, two years after they stopped smoking marijuana.

Teens who were heavy marijuana users -- smoking it daily for about three years -- had an abnormally shaped hippocampus and performed poorly on long-term memory tasks, reports a new Northwestern Medicine study.

The hippocampus is important to long-term memory (also known as episodic memory), which is the ability to remember autobiographical or life events.

The brain abnormalities and memory problems were observed during the individuals' early twenties, two years after they stopped smoking marijuana.

Young adults who abused cannabis as teens performed about 18 percent worse on long-term memory tests than young adults who never abused cannabis.

"The memory processes that appear to be affected by cannabis are ones that we use every day to solve common problems and to sustain our relationships with friends and family," said senior author Dr. John Csernansky, the Lizzie Gilman professor and chair of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine and Northwestern Memorial Hospital.

The study will be published March 12 in the journal Hippocampus.

The study is among the first to say the hippocampus is shaped differently in heavy marijuana smokers and the different looking shape is directly related to poor long-term memory performance. Previous studies of cannabis users have shown either the oddly shaped hippocampus or poor long-term memory but none have linked them.

Previous research by the same Northwestern team showed poor short-term and working memory performance and abnormal shapes of brain structures in the sub-cortex including the striatum, globus pallidus and thalamus.

"Both our recent studies link the chronic use of marijuana during adolescence to these differences in the shape of brain regions that are critical to memory and that appear to last for at least a few years after people stop using it," said lead study author Matthew Smith, assistant professor of psychiatry and behavioral sciences at the Feinberg School of Medicine.

The longer the individuals were chronically using marijuana, the more abnormal the shape of their hippocampus, the study reports. The findings suggest that these regions related to memory may be more susceptible to the effects of the drug the longer the abuse occurs.

The abnormal shape likely reflects damage to the hippocampus and could include the structure's neurons, axons or their supportive environments.

"Advanced brain mapping tools allowed us to examine detailed and sometimes subtle changes in small brain structures, including the hippocampus," said Lei Wang, also a senior study author and an assistant professor of psychiatry and behavioral sciences at Feinberg. The scientists used computerized programs they developed with collaborators that performed fine mappings between structural MRIs of different individuals' brains.

Subjects took a narrative memory test in which they listened to a series of stories for about one minute, then were asked to recall as much content as possible 20 to 30 minutes later. The test assessed their ability to encode, store, and recall details from the stories.

The groups in the study started using marijuana daily between 16 to 17 years of age for about three years. At the time of the study, they had been marijuana free for about two years. A total of 97 subjects participated, including matched groups of healthy controls, subjects with a marijuana use disorder, schizophrenia subjects with no history of substance use disorders, and schizophrenia subjects with a marijuana use disorder. The subjects who used marijuana did not abuse other drugs.

The study also found that young adults with schizophrenia who abused cannabis as teens performed about 26 percent more poorly on memory tests than young adults with schizophrenia who never abused cannabis.

In the U.S., marijuana is the most commonly used illicit drug, and young adults have the highest -- and growing -- prevalence of use. Decriminalization of the drug may lead to greater use. Four states have legalized marijuana for recreational use, and 23 states plus Washington D.C. have legalized it for medical use.

Because the study results examined one point in time, a longitudinal study is needed to definitively show if marijuana is responsible for the observed differences in the brain and memory impairment, Smith said.

"It is possible that the abnormal brain structures reveal a pre-existing vulnerability to marijuana abuse," Smith said. "But evidence that the longer the participants were abusing marijuana, the greater the differences in hippocampus shape suggests marijuana may be the cause."

Other Northwestern authors include senior author Hans C. Breiter and coauthors Derin J. Cobia, James L. Reilly, Andrea G. Roberts and Kathryn I. Alpert.

The study was funded by the National Institute of Mental Health of the National Institutes of Health, grants R01 MH056584 and P50 MH071616.

Tomado de:Northwestern University. (2015, March 12). Teen cannabis users have poor long-term memory in adulthood. ScienceDaily. Retrieved May 19, 2015 from www.sciencedaily.com/releases/2015/03/150312082906.htm

Cannabis: A new frontier in therapeutics

Wile debate about recreational marijuana use continues, researchers are investigating the effectiveness of cannabis for treating pain, spasticity, and a host of other medical problems. In a symposium organized by the McGill University Health Centre (MUHC) as part of the 2015 American Association for the Advancement of Science Annual Meeting held this week in San Jose, California,  experts from North America and the U.K. share their perspectives on the therapeutic potential of medical cannabis and explore the emerging science behind it.

"We need to advance our understanding of the role of cannabinoids in health and disease through research and education for patients, physicians and policy-makers," says Dr. Mark Ware, director of clinical research at the Alan Edwards Pain Management Unit at the MUHC, in Canada.

As a pain specialist Dr. Ware regularly sees patients with severe chronic pain at his clinic in Montreal, and for some of them, marijuana appears to be a credible option. "I don't think that every physician should prescribe medical cannabis, or that every patient can benefit but it's time to enhance our scientific knowledge base and have informed discussions with patients."

Increasing numbers of jurisdictions worldwide are allowing access to herbal cannabis, and a range of policy initiatives are emerging to regulate its production, distribution, and authorization. It is widely believed that there is little evidence to support the consideration of cannabis as a therapeutic agent. However, several medicines based on tetrahydrocannabinol (THC), the psychoactive ingredient of cannabis, have been approved as pharmaceutical drugs.

Leading British cannabis researcher Professor Roger Pertwee, who co-discovered the presence of tetrahydrocannabivarin (THCV) in cannabis in the 70's, recently published with collaborators some findings of potential therapeutic relevance in the British Journal of Pharmacology. "We observed that THCV, the non-psychoactive component of cannabis, produces anti-schizophrenic effects in a preclinical model of schizophrenia," says Pertwee, professor of Neuropharmacology at Aberdeen University. "This finding has revealed a new potential therapeutic use for this compound."

Neuropsychiatrist and Director of the Center for Medicinal Cannabis Research (CMCR) at the University of California, San Diego Dr. Igor Grant is interested in the short and long-term neuropsychiatric effects of marijuana use. The CMCR has overseen some of the most extensive research on the therapeutic effects of medical marijuana in the U.S. "Despite a commonly held view that cannabis use results in brain damage, meta analyses of extensive neurocognitive studies fail to demonstrate meaningful cognitive declines among recreational users," says Dr. Grant. "Bain imaging has produced variable results, with the best designed studies showing null findings."

Dr. Grant adds that while it is plausible to hypothesize that cannabis exposure in children and adolescents could impair brain development or predispose to mental illness, data from properly designed prospective studies is lacking.

Tomado de sciencedaily.com

FUente: McGill University Health Centre. (2015, February 15). Cannabis: A new frontier in therapeutics. ScienceDaily. Retrieved February 16, 2015 from www.sciencedaily.com/releases/2015/02/150215070209.htm

Cannabis use in adolescence has negative impact on education

A study looks to add more fuel to the heated debate around the use of marijuana, as researchers have linked the frequent use of cannabis among adolescents with reduced educational attainment. The study also links frequent use of the drug with other negative health outcomes, such as suicide attempts.


The study's lead author, Dr. Edmund Silins, says that the results "provide strong evidence that the prevention or delay of cannabis use is likely to have broad health and social benefits."

The team, comprised of researchers from Australia and New Zealand, received funding from the Australian Government National Health and Medical Research Council, and the study has been published in The Lancet Psychiatry.


Many researchers are pushing for cannabis to be used in a therapeutic capacity, as a form of pain relief or to alleviate symptoms of conditions such as multiple sclerosis (MS) and post-traumatic stress disorder(PTSD).

However, study author Richard Mattick believes that moves toward the decriminalization and legalization of cannabis also contribute toward "raising the possibility that the drug might become more accessible to young people."

Outside of legal avenues, cannabis is the most widely used illicit drug worldwide. The National Institute on Drug Abuse (NIDA) report that around 7% of US high-school seniors are daily or near-daily cannabis users, with around 46% having tried the drug at some point during their lifetime.

Although the study uses data from adolescents in Australia and New Zealand, the authors state that the rates of cannabis use are similar across high-income countries. For example, they cite that the rates of cannabis use among adults in Australia and New Zealand are 10% and 15% respectively, compared with a rate of 15% in the US.

Does early cannabis use compromise education?

For the study, the researchers utilized the data of 3,765 participants from three large, long-term longitudinal studies, tracking cannabis use alongside several developmental outcomes from before the age of 17 up to the age of 30.

They recorded the frequency of cannabis use as never, less than monthly, monthly or more, weekly or more, or daily. The researchers chose to record the following developmental outcomes:

• Cannabis dependence
• Completing high school
• Depression
• Obtaining a university degree
• Suicide attempts
• Use of other illicit drugs
• Welfare dependence.

The researchers found significant associations between the frequency of adolescent cannabis use and all of the designated developmental outcomes. After adjusting for potential confounding factors such as socioeconomic status and mental illness, they found that five of the associations remained significant.

Individuals who had used cannabis daily before the age of 17 were 60% less likely to complete high school or obtain a degree than those who had never used cannabis. They were also 18 times more likely to become dependent on cannabis, eight times more likely to use other illicit drugs and seven times more likely to attempt suicide by the age of 25.

Most significantly, the researchers found that the risk of negative developmental outcomes increased relative to the frequency of the cannabis dose. Daily cannabis users experienced the strongest effects of the association.

Impact on reforming legislation


In a linked commentary, Prof. Merete Nordentoft, of the University of Copenhagen, Denmark, explains why these results may have occurred:

"Persistent cannabis use has adverse effects, such as low energy and initiative, and impairment of cognitive functions, and these factors are likely to mediate the harmful effect of cannabis on educational attainment."

The authors say that these findings are consistent with the results of previous studies investigating early cannabis use alongside these developmental outcomes. They suggest that preventing or delaying cannabis use in adolescents could have far-reaching benefits, both socially and with regard to health.

One measure that the authors suggest could be implemented is screening for cannabis use in adolescents as standard practice during visits to doctors, child psychiatrists, school nurses and other health care practitioners. This is due to an estimated lack of self-reporting among adolescent cannabis users.

"Efforts to reform cannabis legislation should be carefully assessed to ensure they reduce adolescent cannabis use and prevent potentially adverse effects on adolescent development," says Dr. Silins.

In spite of this, the authors also acknowledge that within US states where cannabis has been made increasingly available for medical use, there has been no reported increase in use among young people.

The study still urges caution. The landscape is undeniably changing with regard to how cannabis is perceived and utilized, and the authors believe that as this framework changes, the needs of the youth must always be considered in order to prevent adverse developmental outcomes.

Tomado de: Medical News Today. Written by James McIntosh

APA: Regular marijuana use bad for teens' brains

As presented at the Annual Convention of the American Psychological Association

Frequent marijuana use can have a significant negative effect on the brains of teenagers and young adults, including cognitive decline, poor attention and memory, and decreased IQ, according to psychologists discussing public health implications of marijuana legalization at at APA, held in Washington, D.C., in August. 
     “It needs to be emphasized that regular cannabis use, which we consider once a week, is not safe and may result in addiction and neurocognitive damage, especially in youth,” said Krista Lisdahl, PhD, director of the brain imaging and neuropsychology lab at University of Wisconsin-Milwaukee. 
Brain imaging studies of regular marijuana users have shown significant changes in their brain structure, particularly among adolescents, Dr. Lisdahl said. Abnormalities in the brain’s gray matter, which is associated with intelligence, have been found in 16- to 19-year-olds who increased their marijuana use in the past year, she said. These findings remained even after researchers controlled for major medical conditions, prenatal drug exposure, developmental delays, and learning disabilities, she added. 
     “When considering legalization, policymakers need to address ways to prevent easy access to marijuana and provide additional treatment funding for adolescent and young adult users,” she said. She also recommended that legislators consider regulating levels of tetrahydrocannabinol, or THC, the major psychoactive chemical in marijuana, in order to reduce potential neurocognitive effects. 

Tomado de: Reportes de Congresos.  Univadis.com

La marihuana puede resultar beneficiosa en el tratamiento de las enfermedades autoinmunitarias

La marihuana se usa actualmente para fines médicos, entre otros, para aliviar los efectos secundarios de la quimioterapia y tratar el dolor crónico. El "Journal of Biological Chemistry" informó de que científicos estadounidenses han encontrado ahora una posible aplicación nueva: el tratamiento de las enfermedades autoinmunitarias.

Científicos de la Universidad de Carolina del Sur (Columbia) investigaron si el tetrahidrocannabinol (THC) presente en la marihuana es capaz o no de alterar la expresión del ADN a través de vías epigenéticas. Al hacerlo, descubrieron que el THC afecta en realidad a un grupo de moléculas denominadas histonas. El sistema inmunitario, por tanto, queda suprimido.

Normalmente, la supresión del beneficioso sistema inmunitario es una de las consecuencias negativas del uso de la marihuana. Pero en las enfermedades autoinmunitarias, como la artritis, el lupus o la esclerosis múltiple, en las que la inflamación crónica desempeña un papel fundamental, el uso de la marihuana podría ser efectivo, sugieren los investigadores

Tomado de Univadis.com

• Xiaoming Yang, 
• Venkatesh L. Hegde, 
• Roshni Rao, 
• Jiajia Zhang,
• Prakash S. Nagarkatti, 
• and Mitzi Nagarkatti 

Histone modifications are associated with Delta(9)-tetrahydrocannabinol-mediated alterations in antigen-specific T cell responses. J. Biol. Chem. jbc.M113.545210. First Published on May 19, 2014,doi:10.1074/jbc.M113.545210

Cannabis can disrupt fertility in men

Men who take cannabis regularly could impair their ability to father a child. According to a British study published in "Human Reproduction", cannabis changes the shape and size of sperm.

For the study, scientists from the universities of Sheffield and Manchester recruited over 2,200 men from 14 fertility clinics in Great Britain and asked them to complete detailed questionnaires about their lifestyle and medical history. Data on sperm morphology was available from 1,970 men. In 318 of them, less than four per cent of the sperm was of normal size and shape. These men were compared to the other 1,652 people.

The researchers found that men with less than four per cent of "normal" sperm, were nearly twice as likely to have produced the sperm samples during the summer months (June to August), or, if they were younger than 30 years of age, they had used cannabis during the previous three months. However, the morphology of the sperm was better when the subjects had been sexually inactive for more than six days.

Other lifestyle factors such as smoking or drinking did not affect shape and size of the sperm. However, effects on the DNA of the sperm could not be entirely ruled out.

Men with poor sperm morphology were frequently looking for possible factors in their lifestyles that could be causing this, said study author Allan Pacey. "It is therefore reassuring to find that there are very few identifiable risks." He advised cannabis users to stop using the drug if they want to father a child.

Tomado: Univadis.com

Ref:  A: Pacey y cols.  Modifiable and non-modifiable risk factors for poor sperm morphology. Hum. Reprod. (2014)