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RESEARCH BRIEFSWHO Report Reviews World Mental Health CareThere is little evidence one way or the other for the effectiveness of treating either common or severe mental disorders in primary care settings in developing countries, according to a new report from the World Health Organization.
Prevalence of Major Psychiatric Disorders in Primary Health Care
The table gives a global snapshot of some major psychiatric disorders seen in primary health care settings, from the World Health Report 2001. Depression, anxiety, and other mental disorders constitute more than 12 percent of the global burden of disease and affect about one quarter of all patients in primary care settings. Developing nations face greater difficulties in providing appropriate mental health treatment. India, for example, has two to three psychiatrists per million inhabitants compared to 50 to 150 per million in developed countries. Of the 13,000 physicians in mental health settings who serve the 1 billion people in China, only about 3,000 of them are fully trained psychiatrists. "The problem facing poorer countries is to use limited resources to establish a range of strategies and actual service models that can extend mental health services most effectively," writes report author Alex Cohen, HMS instructor in social medicine. "It's almost like making something out of nothing." Since the mid-1970s, WHO policies have encouraged integrating mental health services into primary care settings. No one knows what, if anything, might be working to help those who are suffering, concludes Cohen after reviewing anecdotal descriptions from India, Colombia, Nepal, Iran, Nicaragua, Guinea-Bissau, Tanzania, and Botswana. Common problems plagued all the programs: limited resources, different service models, uneven training, high staff turnover, and inadequate drug supply. Others had more serious problems. In Tanzania, for example, phenobarbital was prescribed for seven times more people than those diagnosed with epilepsy, and psychotropic drugs went to double the number of people diagnosed with psychosis. The lack of evidence does not mean abandoning the policy. "The lack of mental health resources in the developing world makes integration the only realistic option," Cohen writes. "Yet care must be taken in how that policy is implemented." The report offers immediate, practical recommendations such as investing scarce resources in systems of care rather than individual providers and having mental health specialists supervise treatment. Cohen also stresses evaluation of programs for effectiveness. --Carol Cruzan Morton
Glimpsing a Neuron's Quick-Change ArtistryTracking the receptive field of a single neuron is like capturing a fast moving target. At any given moment, the cell responds only to certain stimuli. But as new information enters the brain, it frequently makes adjustments, essentially changing its receptive field. Researchers have tried to track these changes by analyzing a neuron's firing properties over a period of seconds, but a cell changes in milliseconds, rendering such attempts too crude. Emery Brown and his colleagues have devised a way to capture these split-second changes and to provide updates of a neuron's new receptive properties almost as fast as they occur. Building on an engineering paradigm, adaptive signal processing, the researchers developed an algorithm that estimates the current receptive field of a nerve cell by analyzing its firing pattern, or spike train. "We figured out a way to see how the parameters of receptive fields changed as spikes came in and to write an algorithm to update those parameters," said Brown, HMS associate professor of anesthesia at MGH. Applying the algorithm to neurons in the hippocampus, they accurately predicted changes in their receptive fields. "You can see the receptive field grow in real time," he said. The online version of Brown's report, which appears in the Oct. 9 Proceedings of the National Academy of Sciences, is accompanied by real-time displays of neurons' changing receptive fields. Though its primary benefit is to enable researchers to better study plasticity, the ability to more accurately model changes in receptive fields could help usher in a new era of devices to help neurally impaired people. "Eventually, we want to build prosthetics that use neural signals from the brain to guide robotic devices," said Brown. --Misia Landau
Mutation Alters Work of Bacterial EnzymeA team led by Jonathan Beckwith, the American Cancer Society professor of microbiology and molecular genetics at HMS, has discovered a genetic switch in E. coli that modifies the bacterium's ability to survive in hostile environments. The group was studying a strain of E. coli that lacks the two enzymes essential for reducing disulfide bonds, thioredoxin reductase and glutathione reductase. These agents recycle reductive enzymes in order to maintain the highly reducing environment that is characteristic of the cytosol in all cells. The bacteria "need to have an enzyme that does disulfide bond reduction or else they cannot grow," said Daniel Ritz, a research fellow in Beckwith's lab and the paper's first author, which appears in the Oct. 5 Science. But even with their usual machinery broken, some of the bacteria were able to grow at a normal rate. The team identified a mutation that was allowing this strain to avoid the fate of the others, an amplification of a triplet repeat sequence that results in the addition of an amino acid. Surprisingly, the extra amino acid actually changes the function of the protein, peroxiredoxin AhpC, an enzyme that normally helps the bacterium fight oxidative stress by reducing peroxide. The altered protein is a disulfide bond reducer, restoring an essential function to the bacteria. Triplet repeat expansions are implicated in several human diseases, in which they lead to proteins that aggregate or lose function. This is the first time such a mutation has been seen to have a positive effect, allowing a protein to alternate between two enzymatic functions. Other types of switch have been found in bacteria that alter gene expression to evade a host. Beckwith believes that this switch may offer a similar evolutionary advantage, enabling the bacteria to adapt to different stresses in the environment. --Courtney Humphries |
