Poor performance at school could indicate an increased risk of later developing schizophrenia, a study says.
UK and Swedish researchers followed more than 900,000 children born between 1973 and 1983.
The Psychological Medicine paper found getting an E grade in any GCSE-stage exam was linked to a doubling of the small risk of developing schizophrenia.
But a mental health charity said the illness was often linked with high, rather than low, intelligence.
Schizophrenia, which commonly causes people to hear voices and experience paranoid delusions, often becomes evident in the late teens or early 20s.
The researchers, from the Institute of Psychiatry at King's College London, and the Karolinska Institute in Stockholm, looked at Swedish data on exam results taken at the age of 15 or 16.
They then looked at hospital data on admissions for psychotic disorders including schizophrenia after the age of 17.
Sweden has comprehensive national registers, with every individual having their own identification code, so the data could be compared.
The general risk for an adult to be diagnosed with schizophrenia in any given year is seven in 100,000.
Getting an E grade in any of the 16 subjects looked at by the researchers was linked to a doubling of that risk.
The researchers found those with the poorest school performance overall had four times that risk of developing schizophrenia when they were adults.
Other studies have shown that there is a link between schizophrenia and earlier problems with learning or understanding.
However, the researchers said other factors were probably involved.
Writing in the journal, Dr James MacCabe of the Institute of Psychiatry, who led the research team, said: "School performance should not be seen simply as a proxy for intelligence."
The researchers said poor attendance and engagement with education, memory and attention problems as well as issues with organisation, creativity, diligence and social skills could all play a part.
Dr MacCabe said: "Doing badly at school is not a cause of schizophrenia, but it is a marker for something not being quite right several years prior to diagnosis.
"This isn't going to be a way of identifying people at school who are at risk of developing schizophrenia.
"But it could be useful when considering someone who is displaying other potential symptoms of impending psychosis."
But Hilary Caprani, a spokeswoman for the mental health charity Rethink, warned: "It is important to recognise that mental illnesses like schizophrenia are not linked to low intelligence. The opposite is often true.
"There are lots of reasons why young people perform poorly in exams.
"Problems with concentration and mental distress can interfere with studying and these can also be early signs of mental illness - symptoms that commonly begin in late teens.
"The people in the study might have had normal intelligence but started having low-level symptoms that disrupted their schooling."
She added: "The good news is that many people who have psychosis recover and go on to have challenging careers."
Metals in brain seen in world-first images
Scientists at UTS can now view images of metal elements such as iron and zinc in brain and heart tissue by using existing technologies in new ways to pinpoint clinical diagnoses and confirm drug actions for a range of diseases.
Dr Philip Doble speaking at the opening of the Bio-imaging Facility
“Using the latest Inductively Coupled Plasma Mass Spectrometer, researchers place a slice of human tissue on a plate, pop it into a sample chamber, zap it with a laser and create diagnostic images,” said Dr Philip Doble at the opening of the world-first dedicated bio-imaging facility in the UTS Science Faculty.
Developed in collaboration with Agilent Technologies, a leading global provider of analytical instrumentation, the new laboratories use commercially available instruments, consumables and software.
"The tissue sample is vaporised and swept to a plasma at 8000K, which breaks the sample into its elemental components, giving a direct chemical analysis of the entire sample that can be seen as an image rather than as a series of numbers," Dr Doble said.
“Direct sampling of biopsy material for example, reduces the errors that creep in when ordinary sampling techniques are used. The new technique can probe the mechanism, progression and treatment of many diseases, including heart disease and it can detect the spread of cancer such as melanoma in lymph nodes.”
Dr Rudolf Grimm from Agilent Technologies said the new process for examining the trace metals in human tissues had begun by using equipment designed for assaying rocks, although UTS bought its first inductively coupled plasma mass spectrometer for use in forensic science research.
Dr Rudolf Grimm, Agilent Technologies, unveiling the UTS Elemental Bio-imaging Facility
Agilent Technologies will supply new machines as they become available to ensure researchers and students have access to the latest technology.
At the recent launch of the new facility, UTS Vice-Chancellor Professor Ross Milbourne said it would become platform technology for the new research field of metallomics at the University, enabling research that examines metals and their interactions with proteins in the body.
"In collaboration with Stanford University in California, the team has already confirmed the formation of calcium phosphate crystals in the knees of osteoarthritis patients, which was previously surmised from data," Professor Milbourne said.
"The team is now conducting research using the facility into the neuro-degenerative Alzheimer's and Parkinson's diseases," he said.
'Hunger hormone' depression link
High levels of the "hunger hormone" ghrelin have an antidepressant effect, US researchers claim.
Blocking the body's response to ghrelin has been suggested as a weight loss treatment but it may also produce unintended effects on mood, they said.
The Nature Neuroscience study found mice with increased levels of the hormone showed fewer signs of depression and anxiety.
Experts said the idea was interesting but further studies were needed.
Ghrelin is released by the empty stomach into the bloodstream before moving to the brain, where it triggers feelings of hunger.
Treatment with the hormone itself - or a drug designed to cancel its effects - might be able to help both people who are eating too little, such as cancer patients, or those who eat too much, researchers believe.
In the latest study, Dr Jeffrey Zigman and colleagues restricted the food intake of laboratory mice for 10 days, causing their ghrelin levels to quadruple.
Compared with mice who had free access to food, the calorie-restricted mice showed lower levels of depression and anxiety when subjected to mazes and other behaviour tests.
The team also looked at mice genetically engineered to be unable to respond to ghrelin.
When they were fed a restricted-calorie diet they did not experience the antidepressant or anti-anxiety effects.
The researchers found the same thing when they induced higher ghrelin levels by subjecting the mice to stress.
Those mice that could not respond to ghrelin had greater levels of depression-like symptoms than the normal mice.
"Our findings in mice suggest that chronic stress causes ghrelin levels to go up, and that behaviours associated with depression and anxiety decrease when ghrelin levels rise," said Dr Zigman, a researcher at UT Southwestern Medical Center in Dallas.
"An unfortunate side effect, however, is increased food intake and body weight," he added.
He said the results made sense from an evolutionary standpoint, as hunter-gatherers may have had a survival advantage in remaining calm and collected in times of hunger in order for them to successfully find food.
The researchers are now hoping to look at the antidepressant effect of the hormone in conditions such as anorexia.
Professor Stephen Bloom, an expert in appetite regulation at Imperial College London, said it was reasonable to believe that ghrelin had an impact on behavioural responses other than just hunger.
But he said there was a lot of research to be done before it could be confirmed that a hormone released in the stomach can have an effect on mood in the brain.
"The role of ghrelin in the gut and in the brain are likely to be completely different," he said.
Spain treats child phone addicts
Two children in Spain have been admitted to a mental health institution to be treated for addiction to their mobile phones, Spanish media report.
The children, aged 12 and 13, were sent to the clinic by their parents, who said they could not carry out normal activities without their handsets.
They were doing badly at school and lying to relatives in order to get money to spend on their phones.
They have been learning to cope without their phones for three months.
Dr Maite Utges, who runs the Child and Youth Mental Health Centre in Lleida, near Barcelona in north-eastern Spain, said it was the first time the clinic had treated children who were dependent on their mobile phones.
"They both showed disturbed behaviour and this exhibited itself in failure at school. They both had serious difficulties leading normal lives," she was quoted in Spanish papers as saying.
The children had owned their phones for 18 months, and their parents had made little effort to restrict their use before noticing how serious their dependence had become.
'Tip of iceberg'
Dr Jose Martinez-Raga, an expert in addictions, said children who developed a dependency on mobile phones, like those who over-used video games, often became irritable, withdrawn and antisocial, and their school performance deteriorated.
He warned these cases could be the "tip of the iceberg", and that mobile phone addiction "could definitely be a danger in the future".
Fears have been raised in a number of countries about the adverse effects mobile phone use may have on children.
Dr Utges recommended that parents not allow their children to have mobile phones until they reached 16 years of age.
Mental Illness, disorder characterized by disturbances in a person’s thoughts, emotions, or behavior. The term mental illness can refer to a wide variety of disorders, ranging from those that cause mild distress to those that severely impair a person’s ability to function. Mental health professionals sometimes use the terms psychiatric disorder or psychopathology to refer to mental illness.
THE EXPERIENCE OF MENTAL ILLNESS
Severe mental illness almost always alters a person’s life dramatically. People with severe mental illnesses experience disturbing symptoms that can make it difficult to hold a job, go to school, relate to others, or cope with ordinary life demands. Some individuals require hospitalization because they become unable to care for themselves or because they are at risk of committing suicide. (THE EXPERIENCE OF MENTAL ILLNESS)
The symptoms of mental illness can be very distressing. People who develop schizophrenia may hear voices inside their head that say nasty things about them or command them to act in strange or unpredictable ways. Or they may be paralyzed by paranoia—the deep conviction that everyone, including their closest family members, wants to injure or destroy them. People with major depression may feel that nothing brings pleasure and that life is so dreary and unhappy that it is better to be dead. People with panic disorder may experience heart palpitations, rapid breathing, and anxiety so extreme that they may not be able to leave home. People who experience episodes of mania may engage in reckless sexual behavior or may spend money indiscriminately, acts that later cause them to feel guilt, shame, and desperation. (THE EXPERIENCE OF MENTAL ILLNESS)
Other mental illnesses, while not always debilitating, create certain problems in living. People with personality disorders may experience loneliness and isolation because their personality style interferes with social relations. People with an eating disorder may become so preoccupied with their weight and appearance that they force themselves to vomit or refuse to eat. Individuals who develop post-traumatic stress disorder may become angry easily, experience disturbing memories, and have trouble concentrating. (THE EXPERIENCE OF MENTAL ILLNESS)
Experiences of mental illness often differ depending on one’s culture or social group, sometimes greatly so. For example, in most of the non-Western world, people with depression complain principally of physical ailments, such as lack of energy, poor sleep, loss of appetite, and various kinds of physical pain. Indeed, even in North America these complaints are commonplace. But in the United States and other Western societies, depressed people and mental health professionals who treat them tend to emphasize psychological problems, such as feelings of sadness, worthlessness, and despair. The experience of schizophrenia also differs by culture. In India, one-third of new cases of schizophrenia involve catatonia, a behavioral condition in which a person maintains a bizarre statuelike pose for hours or days. This condition is rare in Europe and North America. (THE EXPERIENCE OF MENTAL ILLNESS)
With appropriate treatment, most people can recover from mental illness and return to normal life. Even those with persistent, long-term mental illnesses can usually learn to manage their symptoms and live productive lives. (THE EXPERIENCE OF MENTAL ILLNESS)