Category: Disorders and Syndromes

— Human speech comes in countless varieties: When people talk to close friends or partners, they talk differently than when they address a physician. These differences in speech are quite subtle and hard to pinpoint.

In a recent special issue of the journal Frontiers in Human Neuroscience, Johanna Derix, Dr. Tonio Ball, and their colleagues from the Bernstein Center and the University Medical Center in Freiburg report that they were able to tell from brain signals who a person was talking to. This discovery could contribute to the further development of speech synthesizers for patients with severe paralysis.

In contrast to the experimental research common in human neuroscience, the scientists studied natural, non-experimental behavior. Patients who, for medical reasons, had electrodes implanted underneath their skull allowed their brain activity to be recorded during daily life in the hospital. The Freiburg researchers compared data recorded during natural conversations that the patients had with their physicians and their life partners. They found pronounced differences in the anterior temporal lobe, a brain area well known for its significance in social interaction. Several components of neural signals that are detectable on the brain surface can convey such information.

"This study is only the first step towards elucidating the neural basis of human everyday behavior," explains the neuroscientist and physician Tonio Ball. "Such investigations will become especially important in developing new neurotechnological treatment options for patients with impaired motor and language functions that work in real life situations." The restoration of speech production becomes necessary in some forms of neurological diseases and chronic paralysis. A computer could synthesize speech for patients suffering from such conditions by using their brain signals. Information on who the patient is addressing could help the device to select the degree of formality — and to prevent it from calling the doctor "darling."

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Journal Reference:

1. Johanna Derix, Olga Iljina, Andreas Schulze-Bonhage, Ad Aertsen, Tonio Ball. 'Doctor' or 'darling'? Decoding the communication partner from ECoG of the anterior temporal lobe during non-experimental, real-life social interaction. Frontiers in Human Neuroscience, 2012; 6 DOI: 10.3389/fnhum.2012.00251

 The world continues to be a noisy place, and Purdue University researchers have found that all that background chatter causes the ears of those with hearing impairments to work differently.

"When immersed in the noise, the neurons of the inner ear must work harder because they are spread too thin," said Kenneth S. Henry, a postdoctoral researcher in Purdue's Department of Speech, Language and Hearing Sciences. "It's comparable to turning on a dozen television screens and asking someone to focus on one program. The result can be fuzzy because these neurons get distracted by other information."

The findings, by Henry and Michael G. Heinz, an associate professor of speech, language and hearing sciences, are published as a Brief Communication in Nature Neuroscience. The work was funded by the National Institutes of Health and the National Institute on Deafness and Other Communication Disorders.

"Previous studies on how the inner ear processes sound have failed to find connections between hearing impairment and degraded temporal coding in auditory nerve fibers, which transmit messages from the inner ear to the brain," said Heinz, who studies auditory neuroscience. "The difference is that such earlier studies were done in quiet environments, but when the same tests are conducted in a noisy environment, there is a physical difference in how auditory nerve fibers respond to sound."

Hearing loss, suffered in varying degrees by 36 million American adults, means there is damage to sensory cells in the cochlea and to cochlear neurons as well. The cochlea is the part of the inner ear that transforms sound into electrical messages to the brain.

In this study, the researchers measured a variety of physiological markers in chinchillas, some with normal hearing and others with a cochlear hearing loss, as they listened to tones in quiet and noisy environments. Chinchillas are used because they have a similar hearing range to humans, and background noise is used in the study to simulate what people would hear in a crowded room.

"The study confirmed that there is essentially no change, even for those with hearing loss, in terms of how the cochlear neurons are processing the tones in quiet, but once noise was added, we did observe a diminished coding of the temporal structure," Henry said.

The researchers focused on coding of the temporal fine structure of sound, which involves synchrony of neural discharges to relatively fast fluctuations in sound pressure. Both coding of fast fine structure information and coding of slower envelope fluctuations are critical to perception of speech in everyday listening environments.

"When noise was part of the study, there was a reduction in how synchronized the neurons were with the temporal fine structure," Henry said.

The auditory system filters sound into a number of channels that are tuned to different frequencies, and those channels vary based on their frequency tuning. In a normal system, the channels are sharp and focused, but they get broader and more scattered with hearing impairment.

"Now that we know a major physiological effect from hearing loss is that the auditory nerve fibers are particularly distracted by background noise, this has implications for research and clinical settings," said Heinz, who also has a joint appointment in biomedical engineering. "For example, most audiology testing, whether it is lab research or hearing-loss screenings, takes place in a quiet environment, but testing noisy, more realistic backgrounds is necessary to truly understand how the ear is processing sound. This also could influence the design of hearing aids and assistive technologies.

"Designers are often working on improving the temporal coding of the signal, but this research suggests that a primary focus should be on improving noise-reduction algorithms so the hearing aid provides a clean signal to the auditory nerve. Other ways people can reduce background noise include induction-loop hearing systems, which are used in churches and other public settings to provide a cleaner signal by avoiding room noise."

Next, the researchers plan to expand the study to focus on more real-world noises and coding of slower envelope information in sound.

"Additional study is certainly needed, and there are others who are also looking at the role the central nervous system plays, too," Henry said. "But ultimately, we found that hearing loss degrades temporal coding of sounds in background noise in the cochlea, the most peripheral level of auditory processing."

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Journal Reference:

1. Kenneth S Henry, Michael G Heinz. Diminished temporal coding with sensorineural hearing loss emerges in background noise. Nature Neuroscience, 2012; DOI: 10.1038/nn.3216

The brain is a notoriously difficult organ to treat, but Johns Hopkins researchers report they are one step closer to having a drug-delivery system flexible enough to overcome some key challenges posed by brain cancer and perhaps other maladies affecting that organ.

In a report published online on Aug. 29 in Science Translational Medicine, the Johns Hopkins team says its bioengineers have designed nanoparticles that can safely and predictably infiltrate deep into the brain when tested in rodent and human tissue.

"We are pleased to have found a way to prevent drug-embedded particles from sticking to their surroundings so that they can spread once they are in the brain," says Justin Hanes, Ph.D., Lewis J. Ort Professor of Ophthalmology, with secondary appointments in chemical and biomolecular engineering, biomedical engineering, oncology, neurological surgery and environmental health sciences, and director of the Johns Hopkins Center for Nanomedicine.

After surgery to remove a brain tumor, standard treatment protocols include the application of chemotherapy directly to the surgical site to kill any cells left behind that could not be surgically removed. To date, this method of preventing tumor recurrence is only moderately successful, in part, because it is hard to administer a dose of chemotherapy high enough to sufficiently penetrate the tissue to be effective and low enough to be safe for the patient and healthy tissue.

To overcome this dosage challenge, engineers designed nanoparticles — about one-thousandth the diameter of a human hair — that deliver the drug in small, steady quantities over a period of time. Conventional drug-delivery nanoparticles are made by entrapping drug molecules together with microscopic, string-like molecules in a tight ball, which slowly breaks down when it comes in contact with water. According to Charles Eberhart, M.D., a Johns Hopkins pathologist and contributor to this work, these nanoparticles historically have not worked very well because they stick to cells at the application site and tend to not migrate deeper into the tissue.

Elizabeth Nance, a graduate student in chemical and biomolecular engineering at Hopkins, and Hopkins neurosurgeon Graeme Woodworth, M.D., suspected that drug penetration might be improved if drug-delivery nanoparticles interacted minimally with their surroundings. Nance first coated nano-sized plastic beads of various sizes with a clinically tested molecule called PEG, or poly(ethylene glycol), that had been shown by others to protect nanoparticles from the body's defense mechanisms. The team reasoned that a dense layer of PEG might also make the beads more slippery.

The team then injected the coated beads into slices of rodent and human brain tissue. They first labeled the beads with glowing tags that enabled them to see the beads as they moved through the tissue. Compared to non-PEG-coated beads, or beads with a less dense PEG coating, they found that a dense coating of PEG allowed larger beads to penetrate the tissue, even those beads that were nearly twice the size previously thought to be the maximum possible for penetration within the brain. They then tested these beads in live rodent brains and found the same results.

The researchers then took biodegradable nanoparticles carrying the chemotherapy drug paclitaxel and coated them with PEG. As expected, in rat brain tissue, nanoparticles without the PEG coating moved very little, while PEG-covered nanoparticles distributed themselves quite well.

"It's really exciting that we now have particles that can carry five times more drug, release it for three times as long and penetrate farther into the brain than before," says Nance. "The next step is to see if we can slow tumor growth or recurrence in rodents." Woodworth added that the team "also wants to optimize the particles and pair them with drugs to treat other brain diseases, like multiple sclerosis, stroke, traumatic brain injury, Alzheimer's and Parkinson's." Another goal for the team is to be able to administer their nanoparticles intravenously, which is research they have already begun.

Authors on the paper include Elizabeth Nance, Graeme Woodworth, Kurt Sailor, Ting-Yu Shih, Qingguo Xu, Ganesh Swaminathan, Dennis Xiang, Charles Eberhart and Justin Hanes, all from The Johns Hopkins University.

This work was supported by grants from the National Cancer Institute (R01CA164789 and U54CA151838).

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Journal Reference:

1. E. A. Nance, G. F. Woodworth, K. A. Sailor, T.-Y. Shih, Q. Xu, G. Swaminathan, D. Xiang, C. Eberhart, J. Hanes. A Dense Poly(Ethylene Glycol) Coating Improves Penetration of Large Polymeric Nanoparticles Within Brain Tissue. Science Translational Medicine, 2012; 4 (149): 149ra119 DOI: 10.1126/scitranslmed.3003594

Have you ever wondered why some people find it so much easier to stop smoking than others? New research shows that vulnerability to smoking addiction is shaped by our genes. A study from the Montreal Neurological Institute and Hospital — The Neuro, McGill University shows that people with genetically fast nicotine metabolism have a significantly greater brain response to smoking cues than those with slow nicotine metabolism.

Previous research shows that greater reactivity to smoking cues predicts decreased success at smoking cessation and that environmental cues promote increased nicotine intake in animals and humans. This new finding that nicotine metabolism rates affect the brain's response to smoking may lead the way for tailoring smoking cessation programs based on individual genetics.

Smoking cues, such as the sight of cigarettes or smokers, affect smoking behavior and are linked to relapse and cigarette use. Nicotine metabolism, by a liver enzyme, also influences smoking behavior. Variations in the gene that codes for this enzyme determine slow or fast rates of metabolism and therefore, the level of nicotine in the blood that reaches the brain. In the study smokers were screened for their nicotine metabolism rates and their enzyme genotype. Participants were aged 18 — 35 and smoked 5-25 cigarettes daily for a minimum of 2 years. People with the slowest and fastest metabolism had their brain response to visual smoking cues measured using functional MRI. Fast metabolizers had significantly greater response to visual cigarette cues than slow metabolizers in brain areas linked to memory, motivation and reward, namely the amygdala, hippocampus, striatum, insula, and cingulate cortex.

"The finding that nicotine metabolism rate has an impact on the brain's response to smoking cues supports our hypothesis that individuals with fast nicotine metabolism rates would have a greater brain response to smoking cues because of close coupling in everyday life between exposure to cigarettes and surges in blood nicotine concentration. In other words they learn to associate cigarette smoking with the nicotine surge," says clinician-scientist Dr. Alain Dagher, lead investigator at The Neuro. "In contrast, individuals with slow metabolism rates, who have relatively constant nicotine blood levels throughout the day, are less likely to develop conditioned responses to cues. For them, smoking is not associated with brief nicotine surges, so they are smoking for other reasons. Possibilities include maintenance of constant brain nicotine levels for cognitive enhancement (ie, improved attention, memory), or relief of stress or anxiety."

Future research could focus on improving smoking cessation methods by tailoring treatments for different types of smokers. One possibility is to measure the rate of nicotine metabolism as part of the therapeutic decision-making process. For example, targeting cue-induced relapse risk may not help those with slow nicotine metabolism, who are more likely to benefit from long-acting cholinergic drugs such as the nicotine patch, consistent with previous clinical trials. Conversely the use of non-nicotine based therapies aimed at reducing craving may help fast metabolizers, as demonstrated for buproprion, an anti-depressant that has been used for smoking cessation.

This research was supported by the Canadian Tobacco Control Research Initiative (AD), Fonds de Recherche en Santé du Québec (AD), and the Canadian Institutes of Health Research.

General practitioners are not always using the most comprehensive and reliable online resources to support them in treating patients with the debilitating hearing condition tinnitus, researchers have found.

The study looked at the 10 main websites used by GPs to get information on clinical practice and found that the two best websites for assessing or managing tinnitus — Map of Medicine and the British Tinnitus Association (BTA) — were rarely used by family doctors, with only two per cent logging on to access their pages.

The research, which involved a team of experts from The University of Nottingham, Nottingham Trent University and the National Institute for Health Research (NIHR) National Biomedical Research Unit in Hearing, is published in the latest edition of the journal BMC Medical Informatics and Decision Making.

Dr Derek Hoare, Senior Research Fellow at The University of Nottingham and the NIHR National Biomedical Research Unit in Hearing, said: "We found that there are better options for sources of online information than those currently used by most GPs. Map of Medicine in particular used a rigorous and explicit approach to reporting making its sources of information very transparent and reliable, while The British Tinnitus Association website came out top for the quality of information it currently provides on treatment choice. Despite this, these two websites are rarely used by GPs.

"However, when we analysed the content of the group of websites we found that all were lacking a number of details relating to either assessing or managing tinnitus and so GPs may have to use a combination of websites to be fully informed. Our report also offers a range of recommendations that will help providers of online tinnitus websites to improve their resources."

Tinnitus, a condition in which patients hear a persistent ringing, hissing or buzzing sound in their ears, affects around 10 per cent of the population and is often associated with other illnesses including stress, anxiety, insomnia, depression and communication difficulties.

Patients usually access NHS services such as neurotology or audiological rehabilitation through their GPs. However, a recent national survey of GPs by the research team highlighted that many feel their knowledge of tinnitus is limited and they need better guidelines on how to effectively assess, diagnose and refer their patients.

In addition, patients with hearing problems expressed concern of poor GP awareness of the condition and other healthcare professionals such as audiologists highlighted inappropriate referrals received from GPs.

As tinnitus is seen to affect a relatively low number of patients at GP surgeries, many doctors are turning to the internet for information on the condition rather than spending resource on specialist training.

However, while the internet can provide instant access to a diverse range of sources, the volume of information available can often make it difficult for GPs to discern between the sites offering sound advice on the management of the condition and those which are inaccurate and unreliable — a Google search of 'tinnitus treatment' generates 11 million results alone.

The research analysed the content of 10 of the sites most commonly used by GPs — which included commercial, charity and Government-run websites — and used a specialist healthcare information score called DISCERN to rate the quality of the information they offered and their usability.

The study found that the Map of Medicine, ranked highest overall for quality and reliability despite achieving a low score for information on the management of tinnitus. Conversely, the BTA site, which was ranked in second place, had one of the highest scores on information on management choices.

The results indicate that GPs would have to visit at least two websites to gather all the information recommended by the Department of Health for good practice in tinnitus care, which is unlikely to happen in a busy practice.

Ironically, the lowest rated website was the NHS patient health information site NHS Choices. Both the highest and the lowest websites were accredited by The Information Standard.

The report recommends that GPs use both the Map of Medicine and the BTA sites as education tools on tinnitus, or more simply, to use the good practice guide on tinnitus produced by the Department of Health.

The research will also offer valuable information for websites providing information on tinnitus on how they can improve their service and Action on Hearing Loss has already gathered the preliminary findings to be incorporated into a forthcoming overhaul of its website.

— Although mothers are usually the ones who have "the birds and the bees" talks with their children, with targeted prompting and guidance, fathers will also step up to the plate. That's the finding of a study in the American Journal of Health Promotion that analyzed mothers' and fathers' responses to a public health campaign about the benefits of having parent-child talks about delaying sexual activity.

"Our findings show that fathers can increase communication frequency on a potentially awkward topic. Then, as their children age and even more important and sensitive topics come up, these fathers will have developed the kind of relationship with their children that can help conversation flow more smoothly," lead study author Jonathan Blitstein, Ph.D., a research psychologist at RTI International, an independent, not-for-profit research institute in North Carolina.

The 18-month study utilized data from the Parents Speak Up National Campaign (PSUNC). Results show that fathers of pre-adolescent and adolescent children exposed to a multi-media campaign increased their communication efforts compared to the control group. Mothers exposed to the same campaign did not increase their communication significantly, perhaps because they were already engaging in these discussions.

Engaging in these talks has critical implications the authors wrote, since previous studies show such conversations can also influence other positive, healthier sexual behaviors such as more use of contraceptives — including condoms — and having fewer sexual partners.

"Parental emotional bonds with children, parental monitoring of adolescent behavior and parental communication about sex are all linked with better sexual health outcomes among youth," said Aubrey Spriggs Madkour, Ph.D., assistant professor in the department of global community health and behavioral sciences at the Tulane University School of Public Health and Tropical Medicine.

"Public service announcements or PSAs can reach fathers 'where they are,' and hold great promise for engaging them in these important discussions with their children," she said.

Madkour noted that the present study was conducted under more tightly controlled conditions than may be expected in a public rollout of a PSA. For example, campaign materials were sent directly to parents, who also received prompts to watch them.

"As a next step in the research, researchers will need to demonstrate that in real world conditions, where parents may or may not see or dedicate their attention to the PSAs, the effects of the campaign are also positive," Madkour said.

Study findings may open the door for effective communication around other risky behaviors, noted Blitstein. "It's a great opportunity for fathers to get more involved. So why don't they? We don't really have that answer, but we shouldn't feed the belief that mothers have sole responsibility."

Ghrelin is a hormone released by the lining of the stomach that promotes feeding behavior. Decreasing ghrelin levels could potentially help combat obesity — in fact, a vaccine that lowers ghrelin levels in order to reduce appetite is being studied as a treatment for obesity.

However, many people eat as a way to relieve stress. If low ghrelin levels increase stress, its effectiveness as a treatment for obesity may be reduced. In the current issue of Biological Psychiatry, researchers led by Dr. Zane Andrews of Monash University in Australia show that mice with no ghrelin are more anxious after stress, but that administration of endogenous ghrelin prevents the over-anxious response.

Previous studies have indicated that ghrelin can be either anxiety-causing or anxiety-relieving. This new set of studies now reveals that this dual role in anxiety behavior is context-dependent. Under non-stressed conditions, normal mice show mild anxiety relative to mice without ghrelin. Under acute stress, normal mice mount an appropriate ghrelin response to stress and are less anxious than no-ghrelin mice. In other words, stress-induced ghrelin release targets the body's stress system to stimulate a hormonal response that will combat the stress.

Ghrelin promotes the drive for food intake and maintains blood glucose during negative energy balance as well as subserving the rewarding nature of food. "We postulate that, under conditions of acute stress, ghrelin limits excessive anxious behavior by promoting the feeling of reward to ensure appropriate food-seeking behavior and maintain energy homeostasis. Consistent with this idea, studies from Jeff Zigman and colleagues showed that elevated ghrelin during calorie restriction produced anxiolytic responses in a test of anxious behavior," said Andrews.

"We hypothesize that ghrelin suppresses anxiety under acutely stressful conditions to encourage food seeking and maintain appropriate energy homeostasis. Indeed, the importance of ghrelin in controlling stress-induced anxiety might manifest only during conditions of elevated plasma ghrelin, such as negative energy balance and calorie restriction," he continued. "This phenomenon represents an important evolutionary adaptation that maintains food-seeking behavior in the face of acutely stressful environments."

"This study highlights the complexity of approaches for reducing the epidemic in obesity," commented Dr. John Krystal, Editor of Biological Psychiatry. "In this case, low ghrelin levels stimulate anxiety and anxiety is a factor that increases food consumption in humans, particularly sweet and fatty comfort foods. These studies highlight complex relationships between systems in the body and brain that regulate mood and food consumption."

— In a study at the University of California, San Diego and VA San Diego Healthcare, researchers were able to regenerate "an astonishing degree" of axonal growth at the site of severe spinal cord injury in rats. Their research revealed that early stage neurons have the ability to survive and extend axons to form new, functional neuronal relays across an injury site in the adult central nervous system (CNS).

The study also proved that at least some types of adult CNS axons can overcome a normally inhibitory growth environment to grow over long distances. Importantly, stem cells across species exhibit these properties. The work will be published in the journal Cell on Sept. 14.

The scientists embedded neural stem cells in a matrix of fibrin (a protein key to blood clotting that is already used in human neuron procedures), mixed with growth factors to form a gel. The gel was then applied to the injury site in rats with completely severed spinal cords.

"Using this method, after six weeks, the number of axons emerging from the injury site exceeded by 200-fold what had ever been seen before," said Mark Tuszynski, MD, PhD, professor in the UC San Diego Department of Neurosciences and director of the UCSD Center for Neural Repair, who headed the study. "The axons also grew 10 times the length of axons in any previous study and, importantly, the regeneration of these axons resulted in significant functional improvement."

In addition, adult cells above the injury site regenerated into the neural stem cells, establishing a new relay circuit that could be measured electrically. "By stimulating the spinal cord four segments above the injury and recording this electrical stimulation three segments below, we detected new relays across the transaction site," said Tuszynski.

To confirm that the mechanism underlying recovery was due to formation of new relays, when rats recovered, their spinal cords were re-transected above the implant. The rats lost motor function — confirming formation of new relays across the injury.

The grafting procedure resulted in significant functional improvement: On a 21-point walking scale, without treatment, the rats score was only 1.5; following the stem cell therapy, it rose to 7 — a score reflecting the animals' ability to move all joints of affected legs.

Results were then replicated using two human stem cell lines, one already in human trials for ALS. "We obtained the exact results using human cells as we had in the rat cells," said Tuszynski.

The study made use of green fluorescent proteins (GFP), a technique that had never before been used to track neural stem cell growth. "By tagging the cells with GFP, we were able to observe the stem cells grow, become neurons and grow axons, showing us the full ability of these cells to grow and make connections with the host neurons," said first author Paul Lu, PhD, assistant research scientist at UCSD's Center for Neural Repair. "This is very exciting, because the technology didn't exist before."

According to the researchers, the study makes clear that early-stage neurons can overcome inhibitors present in the adult nervous system that normally work to maintain the elaborate central nervous system and to keep cells in the adult CNS from growing aberrantly.

Additional contributors to the study include Yaozhi Wang, Lori Graham, Karla McHale, Mingyong Gao, Di Wu, John Brock, Armin Blesch, Ephron S. Rosenzweig, Binhai Zheng and James M. Conner, UCSD Department of Neurosciences; Leif A. Havton, UCLA Department of Neurology; and Martin Marsala, UCSD Department of Anesthesiology.

The work was supported by the Veterans Administration, National Institutes of Health (NS09881), Canadian Spinal Research Organization, The Craig H. Neilsen Foundation, and the Bernard and Anne Spitzer Charitable Trust.

rugs prescribed to treat anxiety, depression and insomnia may increase patients' risk of being involved in motor vehicle accidents, according to a recent study, published in the British Journal of Clinical Pharmacology. Based on the findings, the researchers suggested doctors should consider advising patients not to drive while taking these drugs.

Psychotropic drugs affect the way the brain functions and can impair a driver's ability to control their vehicle. Research on the links between psychotropic medication and driving accidents has focused on benzodiazepines, which have been used to treat anxiety and insomnia. Perhaps the best known of these drugs is diazepam. Newer Z-drugs, used to treat insomnia, have received less attention, as have antidepressants and antipsychotics.

To understand the effects of a wider spectrum of psychotropic drugs on driving accidents, the authors compared drug use in two groups of people identified using medical records from the Taiwanese national health insurance programme. The first group included 5,183 people involved in motor vehicle accidents. The second group included 31,093 people, matched for age, gender and the year of vehicle accidents, who had no record of being involved in motor vehicle accidents. In general, those involved in accidents were more likely to have been taking psychotropic drugs, whether they had been taking them for one month, one week or one day.

The results suggest that the increased risk associated with benzodiazepines is mirrored in both Z-drugs and antidepressants. However, antipsychotics were not associated with an increased risk of motor vehicle accidents, even among those taking higher doses.

"Our findings underscore that people taking these psychotropic drugs should pay increased attention to their driving performance in order to prevent motor vehicle accidents," said lead researcher, Hui-Ju Tsai, who is based at the National Health Research Institutes in Zhunan, Taiwan. "Doctors and pharmacists should choose safer treatments, provide their patients with accurate information and consider advising them not to drive while taking certain psychotropic medications."

The research strengthens the findings of previous reports that have assessed the risk associated with individual psychotropic drugs. It also provides more evidence on the link between dose and driving performance, showing that higher doses are associated with a higher risk of an accident. "Our data demonstrated significant dose effects for antidepressants, benzodiazepine and Z-drugs," said Tsai. "This suggests that taking a higher dosage poses a greater danger to those intending to drive."

The authors recommend that patients do not stop taking their medication, but if concerned should consult their doctor.

Men with divorced parents are significantly more likely to suffer a stroke than men from intact families, shows a new study from the University of Toronto.

The study, to be published this month in the International Journal of Stroke, shows that adult men who had experienced parental divorce before they turned 18are three times more likely to suffer a stroke than men whose parents did not divorce. Women from divorced families did not have a higher risk of stroke than women from intact families.

"The strong association we found for males between parental divorce and stroke is extremely concerning," says lead author Esme Fuller-Thomson, Sandra Rotman Chair at University of Toronto's Factor-Inwentash Faculty of Social Work and Department of Family and Community Medicine. "It is particularly perplexing in light of the fact we excluded from our study individuals who had been exposed to any form of family violence or parental addictions. We had anticipated that the association between the childhood experience of parental divorce and stroke may have been due to other factors such as riskier health behaviors or lower socioeconomic status among men whose parents had divorced," explains University of Toronto recent graduate and co-author Angela Dalton. "However, we controlled statistically for most of the known risk factors for stroke, including age, race, income and education, adult health behaviors (smoking, exercise, obesity, and alcohol use) social support, mental health status and health care coverage. Even after these adjustments, parental divorce was still associated with a threefold risk of stroke among males." Researchers cannot say with certainty why men from divorced families had triple the risk of stroke, but one possibility lies in the body's regulation of cortisol, a hormone associated with stress.

Fuller-Thomson explains the elevated rate of stroke could be linked to a process known as biological embedding. "It is possible that exposure to the stress of parental divorce may have biological implications that change the way these boys react to stress for the rest of their lives," says Fuller-Thomson.

As with all scientific research, it is essential for many researchers to replicate findings from this study in prospective studies before it is safe to draw any conclusions about causality. Fuller-Thomson notes that eventually, the results of this study could potentially affect current stroke education policy. "If these findings are replicated in other studies," says Fuller Thomson, "then perhaps health professionals will include information on a patient's parental divorce status to improve targeting of stroke prevention education."

Internationally, stroke and other cerebrovascular diseases account for 10 per cent of deaths, making stroke the second leading cause of death.