An outbreak of plague has been occurring in Madagascar, with more than 2,000 cases and 170 deaths reported since August 2017.
This island nation is one of the few remaining hotspots for plague in the world, with cases usually reported between September and April each year.
But this outbreak has been unusual, as it has affected many different areas in Madagascar, including heavily populated cities.
What is plague, and how is it treated?
Plague is a serious disease caused by the bacteria Yersina pestis. It has a high death rate if untreated. There are several different clinical forms, including bubonic plague (affecting the lymph nodes), pneumonic plague (affecting the lungs) and septicaemic plague (involving the bloodstream).
Outside of outbreak situations, deaths from plague are usually due to delays in recognition and diagnosis, rather than a lack of treatment options. Although antibiotic resistant strains have been described, plague can generally be treated with a number of commonly available antibiotics.
Why does plague still exist?
Plague was responsible for hundreds of millions of deaths in three devastating pandemics, including the Plague of Justinian in the 6th century, the Black Death in the 14th century, and the Third Pandemic that originated in China in the 19th century.
In these pandemics, it’s generally thought plague was introduced by rats (often transported on ships) then transmitted to local rats in domestic settings. Fleas then transmit the bacterium between infected rats and humans. But there’s still some debate on the transmission pathways of plague in these pandemics. The classical cycle between an animal reservoir (rats) to humans through an insect vector (fleas) is common to many animal-associated infectious diseases, known as zoonoses.
The pattern of plague cases seems to have changed to a more complex ecology over the past 50 years. There has been a shift in cases from Asia to Africa and the re-emergence of disease in other areas such as the United States.
It’s now recognised there are many potential pathways of transmission from animals to humans in different settings. In the US, plague is thought to be transmitted from wild rodents in rural areas, such as prairie dogs and rock squirrels.
In recent years, there’s been interest in the impact of climate change on the potential for outbreaks. The prevalence of plague in animals in Kazakhstan is associated with higher temperatures in spring and rainfall in summer, as are outbreaks in the US. Tree ring studies also suggest similar climatic conditions may have triggered the Black Death and the Third Pandemic.
How can it be controlled?
Modern plague control includes finding cases and treating them, and where cases are detected, clearing homes of fleas using insecticides. Plague cases in hospitals need to be cared for safely to prevent spread to health care workers and other patients.
In affected communities, people should act to keep rats out of homes. This includes making sure food is stored and disposed of safely. Avoiding bites from fleas is also important, using insect repellents and ridding animals of fleas. Although rat control using poisons can also be used, this should only be done after fleas have been controlled, as fleas can leave dying rats and make things worse.
At a national and international level, systems to respond to outbreaks are required to make sure the public receives reliable information, to deploy logistics and resources to where they are required, and co-ordinate the various national and international organisations involved in the response.
How easily can it spread between countries?
Although the concept of quarantine arose from efforts to control plague spread, travel and trade restrictions are not often warranted given their potential economic impact. The wider fallout from outbreaks can be severe. For example, a relatively small outbreak, mostly localised to the city of Surat in India in 1994, provoked widespread panic. This resulted in a national collapse in tourism and trade that was estimated to cost up to US$2 billion.
In this current outbreak, only the Seychelles has implemented travel bans, and it’s thought the risk of transmission is low. Few confirmed cases have been reported in travellers from Madagascar during the current outbreak.
The World Health Organisation has been working with neighbouring countries to improve preparedness efforts. This includes improving surveillance at airports and sea ports, developing contingency plans and pre-positioning of antibiotics and protective equipment.
What is the future for plague?
It’s not possible to eradicate plague, as it is widespread in wildlife rodents outside the sphere of human influence. Outbreaks generally are managed reactively by “firefighting teams” deployed to clear houses of fleas, identify and treat cases and give pre-emptive treatment to contacts at risk.
A more preventative approach, such as the identification of areas at risk using climate models and animal surveys to focus flea and rat control efforts would be better. But this requires a better understanding of transmission pathways in each region where disease persists.
Australia’s productivity growth has been stagnant for over a decade and, according to a new report, our health policies and programs could be partly to blame. Released today, the Productivity Commission report also highlights how the health-care sector (among others) could play a starring role in improving productivity.
The commission has offered a short list of thematic directions for reform. In health these include eliminating low-value services that have uncertain clinical impacts, changing the way services are delivered to focus more on the patient, and moving away from a community pharmacy model to more automatic dispensing in a greater range of more convenient locations.
The underlying message is that productivity growth is essential if Australia is to expand its economy, generate opportunities for real income growth and raise community living standards.
But as a Productivity Commission discussion paper released last November noted, there is a justified global anxiety that growth in productivity — and in income and well-being, which are inextricably linked to it over the longer term — has slowed or stopped. Across the OECD, growth in GDP per hour worked was lower in the decade to 2016 than in any decade from 1950.
The commission notes that labour productivity has been rising, but that has more to do with greater capital investment than more efficient workforce practices.
The report also highlights a change in thought about productivity. The emphasis has shifted from the need to produce goods more cheaply to improving our human capital – the knowledge, skills and work practices of our community – and delivering more efficient and effective health, education and related services.
The change recognises that Australia is now predominantly a service economy, that health care is a significant economic service, and that the productivity of our workforce, including its health, needs to underpin our economic growth.
This is similar to that of New Zealand and the United Kingdom, less than Canada and far less than the United States – which is an international outlier at over 17% of its total domestic output. Add aged care and disability services, and the commission puts the figure at 13% of Australia’s GDP.
We continue to spend ever more on health, in real (inflation-adjusted) terms, both as taxpayers and as consumers. But are we getting good value for our money? An inefficient health system, wrongly priced services and poorly designed system incentives all drag on the cost of health care and on the productivity of a very large sector of the economy.
A decade ago, the health-care and social-assistance sector employed nearly 1.07 million people. This was a little less than retailing (1.21 million) and a little more than manufacturing (1.03 million). The health sector employed 10.3% of the Australian workforce.
Fast forward to 2017 and retail employment has stayed relatively stable at 1.26 million and manufacturing has declined to 0.9 million. In contrast, health care and social assistance has risen to 1.64 million – 13.3% of total employment.
Any opportunity to increase the efficiency of the health workforce will translate directly to greater labour productivity for the economy as a whole. And its effectiveness can be improved, in part by education and training, which improves the skills of our doctors, nurses, allied health workers and others to work collaboratively to deliver patient-centred care. This is the subject of an independent review for the COAG Health Council by this article’s author.
The actual productivity of the health workforce, unfortunately, is notoriously hard to measure. This is due in no small part to the lack of market forces and to wage costs that are often negotiated between unions and their employers – the governments.
The Productivity Commission’s forthcoming report on improving markets and competition in health and other human services will hopefully offer useful guidance on what reforms are needed in some of these sectors.
Workforce health is an important part of our human capital
A third role for a more efficient and effective health sector is to contribute to improving the health of the workforce overall. Education and health are recognised as the two most significant building blocks of human capital. Making the most of our human capital is a central message of the OECD’s research on productivity.
There is also ample evidence, including in the new Productivity Commission report, that poor health leads to poor labour market outcomes. A 2013 study into disadvantage in Australia concluded that people with long-term health conditions are likely to experience deep and persistent disadvantage, but, equally, disadvantage can lead to poor health.
Back to the future
The challenge remains to reform the health system, and its workforce in particular, so that practitioners, administrators and others have the skills, knowledge and professional attributes to meet the emerging health-care needs of our community.
As the Australian Institute of Health and Welfare points out in its latest review of Australia’s health, the community’s burden of disease is changing. There is now a greater need for longer-term integrated care to deliver services for those with chronic diseases, the elderly, those with dementia, disability and poor mental health, and to provide services to those in rural areas and remote communities.
The message in this latest report is welcome, but unfortunately it is not entirely new. A Productivity Commission report over a decade ago made the point that Australia’s growth potential will depend increasingly on making the best use of our human capital.
One of the aspirations at that time was for an agreed agenda of integrated health services reform within a national framework. It was seen as a way of adding much-needed impetus to overcoming long-standing structural problems that prevented the health-care system from performing to its potential.
Little progress has been made since then. Hence this report is important in reinforcing the message that the next big gains in productivity will need to come from reforming the delivery of health and education. Let’s hope the call for a shared agenda of reforms is taken up more actively than experience to date might suggest.
You’ve probably heard of mindfulness. These days, it’s everywhere, like many ideas and practices drawn from Buddhist texts that have become part of mainstream Western culture.
But a review published today in the journal Perspectives on Psychological Science shows the hype is ahead of the evidence. Some reviews of studies on mindfulness suggest it may help with psychological problems such as anxiety, depression, and stress. But it’s not clear what type of mindfulness or meditation we need and for what specific problem.
The study, involving a large group of researchers, clinicians and meditators, found a clear-cut definition of mindfulness doesn’t exist. This has potentially serious implications. If vastly different treatments and practices are considered the same, then research evidence for one may be wrongly taken as support for another.
At the same time, if we move the goalposts too far or in the wrong direction, we might lose the potential benefits of mindfulness altogether.
So, what is mindfulness?
Mindfulness receives a bewildering assortment of definitions. Psychologists measure the concept in differing combinations of acceptance, attentiveness, awareness, body focus, curiosity, nonjudgmental attitude, focus on the present, and others.
It’s equally ill-defined as a set of practices. A brief exercise in self-reflection prompted by a smart-phone app on your daily commute may be considered the same as a months-long meditation retreat. Mindfulness can both refer to what Buddhist monks do and what your yoga instructor does for five minutes at the start and end of a class.
To be clear, mindfulness and meditation are not the same thing. There are types of meditation that are mindful, but not all mindfulness involves meditation and not all meditation is mindfulness-based.
Mindfulness mainly refers to the idea of focusing on the present moment, but it’s not quite that simple. It also refers to several forms of meditation practices that aim to develop skills of awareness of the world around you and of your behavioral patterns and habits. In truth, many disagree about its actual purpose and what is and isn’t mindfulness.
Another common claim is that mindfulness reduces stress, for which there is limited evidence. Other promises, such as improved mood and attention, better eating habits, improved sleep, and better weight control are not fully supported by the science either.
And while benefits have limited evidence, mindfulness and meditation can sometimes be harmful and can lead to psychosis, mania, loss of personal identity, anxiety, panic, and re-experiencing traumatic memories. Experts have suggested mindfulness is not for everyone, especially those suffering from several serious mental health problems such as schizophrenia or bipolar disorder.
Research on mindfulness
Another problem with mindfulness literature is that it often suffers from poor research methodology. Ways of measuring mindfulness are highly variable, assessing quite different phenomena while using the same label. This lack of equivalence among measures and individuals makes it challenging to generalise from one study to another.
Mindfulness researchers rely too much on questionnaires, which require people to introspect and report on mental states that may be slippery and fleeting. These reports are notoriously vulnerable to biases. For example, people who aspire to mindfulness may report being mindful because they see it as desirable, not because they have actually achieved it.
Only a tiny minority of attempts to examine whether these treatments work compare them against another treatment that is known to work – which is the primary means by which clinical science can show added value of new treatments. And a minority of these studies are conducted in regular clinical practices rather than in specialist research contexts.
A recent review of studies, commissioned by the US Agency for Healthcare Research and Quality, found many studies were too poorly conducted to include in the review and that mindfulness treatments were moderately effective, at best, for anxiety, depression, and pain. There was no evidence of efficacy for attention problems, positive mood, substance abuse, eating habits, sleep or weight control.
What should be done?
Mindfulness is definitely a useful concept and a promising set of practices. It may help prevent psychological problems and could be useful as an addition to existing treatments. It may also be helpful for general mental functioning and well-being. But the promise will not be realised if problems are not addressed.
The mindfulness community must agree to key features that are essential to mindfulness and researchers should be clear how their measures and practices include these. Media reports should be equally specific about what states of mind and practices mindfulness includes, rather than using it as a broad term.
Mindfulness might be assessed, not through self-reporting, but in part using more objective neurobiological and behavioural measures, such as breath counting. This is where random tones could be used to “ask” participants if they are focused on the breath (press left button) or if their mind had wandered (press right button).
Researchers studying the efficacy of mindfulness treatments should compare them to credible alternative treatments, whenever possible. Development of new mindfulness approaches should be avoided until we know more about the ones we already have. Scientists and clinicians should use rigorous randomised control trials and work with researchers from outside the mindfulness tradition.
And lastly, mindfulness researchers and practitioners should acknowledge the reality of occasional negative effects. Just as medications must declare potential side effects, so should mindfulness treatments. Researchers should systematically assess potential side effects when studying mindfulness treatments. Practitioners should be alert to them and not recommend mindfulness treatments as a first approach if safer ones with stronger evidence of efficacy are available.
Only 20 years ago butter was the public villain – contributing to raised cholesterol levels and public concern over an increased risk of heart disease. Now this public perception seems to have been reversed, and reality cooking shows seem to use butter in every recipe. But what has caused this shift in perceptions and is it based on scientific evidence?
In the domestic market more people buy margarine than butter, with 27% of respondents in an ABS survey eating margarine the day before, and 15% consuming butter.
Do we still need to be concerned about butter’s links to heart disease, and is there any evidence to suggest butter is better for our health compared to margarine? To answer this we first need to look more closely at the make-up of butter and margarine.
Where do our favourite yellow spreads come from?
Butter is made from the processing of cream. The cream is churned until the liquid (buttermilk) separates from the fat solids. These fat solids are then rinsed, a little salt added, and shaped to form the butter we all love.
Margarine was first developed in France by Napoleon as a substitute for butter to feed the armed forces and lower classes. Margarine is made from vegetable oils, beta-carotene (added for colour), emulsifiers (to help the oil and water mix), salt and flavours (which can include milk solids). Vitamins A and D are also added to the same level present in butter.
Any diet app will tell you margarine has about 10-15% fewer kilojoules than butter. But whether this is significant will largely depend on the amount you consume each day.
A national nutrition survey indicates the average person over 19 years consumes 20 grams a day of spreads (either butter or margarine), which equates to a difference of 100kj. This difference is largely insignificant in a usual daily intake of 8700kj/day.
It’s all in the fatty acids
The significant nutritional difference actually lies in the fatty acid profiles of the two products. The health differences between butter and margarine are based on the presence of different types of fats.
There are three types of fats in our food: saturated fat, monounsaturated fats and polyunsaturated fats. The difference between these lies in their chemical structure. The structure of saturated fats has no double bonds in between the carbon atoms, monounsaturated fats have one double bond between the carbon atoms, and polyunsaturated fats have two or more double bonds between the carbon atoms.
These subtle differences in structure lead to differences in the way our body metabolises these fats, and hence how they affect our health, in particular our heart health.
Margarine can be made from a number of different oils. If coconut oil is used the margarine will be mainly saturated fat, if sunflower oil is used it will mainly be a polyunsaturated fat, and if olive oil or canola oil is used it will mainly be a monounsaturated fat.
Butter, derived from dairy milk, is mainly saturated fat, and the main saturated fats are palmitic acid (about 31%) and myristic acid (about 12%). Studies have shown these raise blood cholesterol levels.
While there is debate in the scientific world about the relative contributions of saturated fats (and the different types of saturated fatty acids) to heart disease, the consensus is that replacing saturated fats with monounsaturated or polyunsaturated fats will lower the risk of heart disease.
There is strong evidence extra-virgin olive oil (a monounsaturated fat) provides strong benefits for heart disease protection – but there isn’t enough extra-virgin olive oil in margarine products to confer this benefit. Using olive-oil-based margarines is going to contribute very little to your daily intake of extra-virgin olive oil.
And this is why it’s confusing for the consumer – despite a margarine being labelled as being made from olive oil, it may contain only small amounts of olive oil and not be as high in monounsaturated fats as expected. It’s best to read the nutrition information panel to determine which margarine is highest in monounsaturated fats.
Another point of difference between butter and margarine is that margarine may contain plant sterols, which help reduce cholesterol levels.
At the end of the day, if you consume butter only occasionally and your diet closely adheres to the Australian guidelines for healthy eating, there is no harm in continuing to do so.
Another option to consider would be the butter blends. These provide the taste of butter while reducing saturated fat intake to half, and they are easier to spread. Of course, if you consume lots of butter, swapping for a low saturated fat margarine is your healthier option – perhaps reserve the butter for special occasions.
If you’re concerned about saturated fat levels in your diet, you should read the nutrition information panel to determine which margarine is lowest in saturated fat, regardless of which oil is used in the product.
As always, people need to base their decision on their family and medical history and obtain advice from their dietitian or GP.
If you are an adult in Australia, the kinds of vaccines you need to get will depend on several factors, including whether you missed out on childhood vaccines, if you are Aboriginal or Torres Strait Islander, your occupation, how old you are and whether you intend to go travelling.
For those born in Australia
Children up to four years and aged 10-15 receive vaccines under the National Immunisation Schedule. These are for hepatitis B, whooping cough, diphtheria, tetanus, measles, mumps, rubella, polio, haemophilus influenzae B, rotavirus, pneumococcal and meningococcal disease, chickenpox and the human papillomavirus (HPV).
Immunity following vaccination varies depending on the vaccine. For example, the measles vaccine protects for a long duration, possibly a lifetime, whereas immunity wanes for pertussis (whooping cough). Boosters are given for many vaccines to improve immunity.
Measles, mumps, rubella, chickenpox, diphtheria and tetanus
People born in Australia before 1966 likely have natural immunity to measles as the viruses were circulating widely prior to the vaccination program. People born after 1965 should have received two doses of a measles vaccine. Those who haven’t, or aren’t sure, can safely receive a vaccine to avoid infection and prevent transmission to babies too young to be vaccinated.
Measles vaccine can be given as MMR (measles-mumps-rubella) or MMRV, which includes varicella (chickenpox). The varicella vaccine on its own (not combined in MMRV) is advised for people aged 14 and over who have not had chickenpox, especially women of childbearing age.
Booster doses of diphtheria, tetanus and whooping cough vaccines, are available free at age 10-15, and recommended at 50 years old and also at 65 years and over if not received in the previous ten years. Anyone unsure of their tetanus vaccination status who sustains a tetanus-prone wound (generally a deep puncture or wound) should get vaccinated. While tetanus is rare in Australia, most cases we see are in older adults.
Pregnant women are recommended to get the diphtheria-tetanus-acellular pertussis vaccine in the third trimester to protect the vulnerable infant after it is born, and influenza vaccine at any stage of the pregnancy (see below under influenza).
Pertussis (whooping cough) is a contagious respiratory infection dangerous for babies. One in every 200 babies who contract whooping cough will die.
It is particularly important for women from 28 weeks gestation to ensure they are vaccinated, as well as the partners of these women and anyone else who is taking care of a child younger than six months old. Deaths from pertussis are also documented in elderly Australians.
The pneumococcal vaccine is funded for everyone aged 65 and over, and recommended for anyone under 65 with risk factors such as chronic lung disease.
Anyone from the age of six months can get the flu (influenza) vaccine. The vaccine can be given to any adult who requests it, but is only funded if they fall into defined risk groups such as pregnant women, Indigenous Australians, peopled aged 65 and over, or those with a medical condition such as chronic lung, cardiac or kidney disease.
Flu vaccine is matched every year to the anticipated circulating flu viruses and is quite effective. The vaccine covers four strains of influenza. Pregnant women are at increased risk of the flu and recommended for influenza vaccine any time during pregnancy.
Health workers, childcare workers and aged-care workers are a priority for vaccination because they care for sick or vulnerable people in institutions at risk of outbreaks. Influenza is the most important vaccine for these occupational groups, and some organisations provide free staff vaccinations. Otherwise, you can ask your doctor for a vaccination.
Any person whose immune system is weakened through medication or illness (such as HIV) is at increased risk of infections. However, live viral or bacterial vaccines must not be given to immunosuppressed people. They must seek medical advice on which vaccines can be safely given.
Australian-born children receive four shots of the hepatitis B vaccine, but some adults are advised to get vaccinations for hepatitis A or B. Those recommended to receive the hepatitis A vaccine are: travellers to hepatitis A endemic areas; people whose jobs put them at risk of acquiring hepatitis A including childcare workers and plumbers; men who have sex with men; injecting drug users; people with developmental disabilities; those with chronic liver disease, liver organ transplant recipients or those chronically infected with hepatitis B or hepatitis C.
Those recommended to get the hepatitis B vaccine are: people who live in a household with someone infected with hepatitis B; those having sexual contact with someone infected with hepatitis B; sex workers; men who have sex with men; injecting drug users; migrants from hepatitis B endemic countries; healthcare workers; Aboriginal and Torres Strait Islanders; and some others at high risk at their workplace or due to a medical condition.
The human papillomavirus (HPV) vaccine protects against cervical, anal, head and neck cancers, as well as some others. It is available for boys and girls and delivered in high school, usually in year seven. There is benefit for older girls and women to be vaccinated, at least up to their mid-to-late 20s.
With ageing comes a progressive decline in the immune system and a corresponding increase in risk of infections. Vaccination is the low-hanging fruit for healthy ageing. The elderly are advised to receive the influenza, pneumococcal and shingles vaccines.
Influenza and pneumonia are major preventable causes of illness and death in older people. The flu causes deaths in children and the elderly during severe seasons.
The most common cause of pneumonia is streptococcus pneumonia, which can be prevented with the pneumococcal vaccine. There are two types of pneumococcal vaccines: pneumococcal conjugate vaccine (PCV) and pneumococcal polysaccharide vaccine (PPV). Both protect against invasive pneumococcal disease (such as meningitis and the blood infection referred to as septicemia), and the conjugate vaccine is proven to reduce the risk of pneumonia.
The government funds influenza (annually) and pneumococcal vaccines for people aged 65 and over.
Shingles is a reactivation of the chickenpox virus. It causes a high burden of disease in older people (who have had chickenpox before) and can lead to debilitating and chronic pain. The shingles vaccine is recommended for people aged 60 and over. The government funds it for people aged 70 to 79.
Travel is a major vector for transmission of infections around the world, and travellers are at high risk of preventable infections. Most epidemics of measles, for example, are imported through travel. People may be under-vaccinated for measles if they missed a dose in childhood.
Anyone travelling should discuss vaccines with their doctor. If unsure of measles vaccination status, vaccination is recommended. This will depend on where people are travelling, and may include vaccination for yellow fever, Japanese encephalitis, cholera, typhoid, hepatitis A or influenza.
Travellers who are visiting friends and relatives overseas often fail to take precautions such as vaccination and do not perceive themselves as being at risk. In fact, they are at higher risk of preventable infections because they may be staying in traditional communities rather than hotels, and can be exposed to risks such as contaminated water, food or mosquitoes.
Aboriginal Australians and Torres Strait Islanders
Indigenous Australians are at increased risk of infections and have access to funded vaccines against influenza (anyone over six months old) and pneumococcal disease (for infants, everyone over 50 years and those aged 15-49 with chronic diseases).
They are also advised to get hepatitis B vaccine if they haven’t already received it. Unfortunately, overall vaccine coverage for these groups is low – between 13% and 50%, representing a real lost opportunity.
Migrants and refugees are at risk of vaccine-preventable infections because they may be under-vaccinated and come from countries with a high incidence of infection. There is no systematic means for GPs to identify people at risk of under-vaccination, but the new Australian Immunisation Register will help if GPs can check the immunisation status of their patients.
The funding of catch-up vaccination has also been a major obstacle until now. In July 2017 the government announced free catch-up vaccinations for children aged 10-19 and for all newly arrived refugees. This covers any childhood vaccine on the National Immunisation Schedule that has been missed.
While this does not cover all under-vaccinated refugees, it is a welcome development. If you are not newly arrived but a migrant or refugee, check with your doctor about catch-up vaccination.
Mental disorders are traditionally seen as rather like flowering bulbs. Above the ground we see their symptoms, but we know their source lies hidden beneath the surface. If we treat the symptoms without addressing the cause – cut off the flower without uprooting the bulb – they will just flower again later.
The idea that each mental disorder has an underlying cause is itself deeply rooted. We imagine that underneath the clinical symptoms of schizophrenia or depression there is an underlying disease entity. If treatment is to be effective and lasting rather than merely symptomatic it must target that concealed origin.
People have had many ideas about the form the unseen cause might take. Medieval physicians imagined a “stone of folly” that had to be surgically removed from a mad person’s head before sanity could prevail. Funnily enough, the best known painting of such an operation, Hieronymus Bosch’s The extraction of the stone of madness, shows the “stone” to be a flower bulb.
More recently, psychiatrists often suppose the hidden cause is neural, such as a brain disease or chemical imbalance. Psychologists sometimes prefer to invoke specific cognitive malfunctions or conflicts. What unifies them is the idea that a cluster of symptoms can be traced back to an underlying pathology.
This way of thinking makes perfect sense in some areas of medicine. A collection of bodily symptoms often points to an underlying disease process. Scarlet fever is revealed by a bright red rash, fever and a sore throat, all caused by an underlying bacterial infection. It would be folly to treat it symptomatically. Pacifying the rash with wet towels, taming the fever with aspirin and drinking tea with honey to soothe the throat would not attack the hidden, microbial cause.
Unfortunately mental disorder is not like infectious disease. Rarely is there a single, identifiable cause underlying a group of symptoms. Most psychiatric symptoms spring from a tangled multiplicity of causes. In addition, many symptoms are not specific to a single condition.
To extend the botanical metaphor, mental disorders are less like flowering bulbs than like bamboo. An interconnected network of underground roots (hidden causes) generates many visible stems (symptoms). No stem can be traced back to a single root, and no root feeds a single stem.
The network approach to mental disorder
If there is no one-to-one link between symptoms and hidden causes, maybe we are better off putting aside the search for those causes. A new way of thinking about mental disorder argues just that, proposing that we focus full attention on symptoms instead.
Rather than seeing symptoms as manifestations of hidden disease entities – as the tip of an iceberg – this “network approach” tells us to examine how symptoms relate to one another. It argues the symptoms of a disorder cluster together not because they share a hidden cause but because they interact with and potentially reinforce one another.
The network approach to mental disorder, developed by Dutch psychologists Denny Borsboom, Angelique Cramer and colleagues, represents each symptom as a node in network. It draws links between these nodes to reveal the symptoms that are most strongly related, such as which ones influence other symptoms most powerfully and extensively.
For example, loss of appetite and weight loss are both symptoms of major depression. If researchers found they were closely related, and appetite loss drives weight loss, then an arrow would be drawn from the former to the latter. By this means a group of dynamically related symptoms can be represented by a network diagram.
Several features of the resulting networks are particularly interesting. Certain symptoms can be shown to be central, related to many others, whereas others are more peripheral. Certain symptoms primarily cause others, whereas some symptoms are primarily caused by others.
Because mental disorders are seen as mutually reinforcing symptoms, clinicians should target central symptoms that cause many others. Successfully treating these symptoms should have broadly beneficial effects. It should reduce other existing symptoms and prevent the spread to new symptoms.
Certain symptoms may also be bridges from one disorder network to another. For example, sleep disturbance among people with post-traumatic stress disorder (PTSD) may cause fatigue, and fatigue may serve as a bridge to the depression network by activating concentration problems and guilt.
Researchers have carried out network analyses of several disorders, using similar computational tools as those used in social network analysis, an approach to mapping relations among people. One study of several substance use problems showed that using the substance more than planned was usually the most central symptom. It was strongly related to having worse withdrawal symptoms and needing more of the substance to get the same effect (“tolerance”).
Several studies have explored anxiety disorders. A study of social anxiety showed that avoidance of potentially threatening social situations was a central symptom and thus a prime target for treatment. Research on PTSD following a catastrophic earthquake in China showed that sleep difficulty and hypervigilance for future threats had especially potent influences on other symptoms.
Turning to depression, a study of short term fluctuations in symptoms revealed the centrality of loss of pleasure in the symptom network. It activated an assortment of other symptoms including sadness, loss of energy and interest in activities and irritability. In contrast, sadness, crying and a loss of interest in sex were incidental.
Another study showed that depressed people whose symptoms were more densely connected were more likely to have persistent depression two years later. This finding accords with the network view that symptoms of mental disorders can be self-reinforcing. People whose symptom networks form a tighter web may therefore have greater difficulty overcoming their problems.
The network approach has several important implications. For researchers, it suggests that the search for single causes of mental disorders is quixotic. Of course, symptoms have an assortment of social and neurobiological sources, but these sources are highly unlikely to be unique to one condition.
For practising psychiatrists and psychologists the network view implies that symptoms should be taken seriously in their own right and not seen merely as pale manifestations of underlying disease. Treatments should directly target particular symptoms, not a fictitious hidden cause.
Boorsboom and Cramer make this point amusingly in regard to major depression.
If [depression] does not exist as an entity that exists independently of its symptoms (like a tumour does), attempting to treat it analogous to the way medical conditions are treated (cutting away the tumour) is like trying to saddle a unicorn.
The network approach also has a strong message for all of us who care about mental health and illness. We should abandon the last vestiges of our belief that mental disorders are best seen as medical diseases. The symptoms of depression, PTSD, or social anxiety don’t point to an underlying disorder. They are the disorder.