General Psychiatry
Twin Studies
By investigating twins, researchers try to answer some of the fundamental questions about the causes of psychiatric illness, in particular the influence of genes (nature) and environment (nurture).
There are two adult twin studies based within the Section of General Psychiatry: The Maudsley Bipolar Twin Study and The Maudsley Schizophrenia Twin Study. The research team working on the Maudsley Schizophrenia Twin Study is also one of nine collaborators on the EUTwinsS Project (European Twin Study Network on Schizophrenia), the largest international study of twins affected by schizophrenia in the world.
Volunteer twins are needed to participate in all three twin studies. The research teams would like to hear from twin pairs who both have schizophrenia or bipolar disorder, from twins where one of the pair has either illness, and from healthy twin pairs. Click on the links below to find out more about each twin study, and about volunteering.
There are other twin studies being carried by other research teams at the IoP: the Twins Early Development Study (TEDS), for example, is based within the Social, Genetic and Developmental Psychiatry Centre and is the largest study of child twins every carried out in the UK. It tracks the development of 15,000 pairs of twins born in England and Wales in 1994, 1995 and 1996 and helps researchers study the most common disorders of childhood – language problems, behaviour problems and learning disabilities. Visit www.teds.ac.uk/home_out.asp to find out more.
- Why investigate twins?
- The Maudsley Bipolar Twin Study
- The Maudsley Schizophrenia Twin Study
- EUTwinsS Project (European Twin Study Network on Schizophrenia)
Why investigate twins?
There are two different types of twins: identical and non-identical. Identical twins are also referred to as monozygotic (from one zygote or egg) while non-identical twins are also referred to as dizygotic (from two eggs) or fraternal twins. Because monozygotic (MZ) twins develop from one fertilised egg, they share exactly the same genetic make-up. As a result, MZ twins are always the same sex. Dizygotic (DZ) twins occur when the mother releases two eggs in the same cycle and both are fertilised. Consequently, DZ twins have the same genetic similarity as any other siblings pair, and can be the same or opposite sex.
Because they share the same genes, identical twins tend to look very similar, especially in the early years of their lives, and can often be mistaken for each other. A common misconception is that identical twins are the ‘same person’, but this is clearly not the case. Despite sharing the same genes, identical twins can grow up to develop quite different tastes and personalities. None the less, they tend to be more similar to each other than any other sibling pair. Identical twins often say they have a lot in common, but also many differences. As their differences cannot be attributed to genetic make-up – which is the same for each twin – they can help shed light on how genes and the environment interact to control development.
Twin studies help researchers untangle genetic, environmental and disease-related influences on brain function and behaviour. If a characteristic is more similar within identical twin pairs (who share 100 per cent of their genetic make up) than within non-identical twin pairs (who share only 50 per cent of their genetic make up), they can infer a genetic influence. The extent of this similarity indicates how much of a role is played by the environment, and how much is played by a person’s genes.
Scientists now know that some of the factors involved in the development of schizophrenia and bipolar disorder are genetic – predisposing genes, for example – and some are environmental – drug use, stressful life events or obstetric complications, for example. They also know that some, but not all, patients with schizophrenia or bipolar disorder have subtle brain and cognitive abnormalities that could be related to the clinical symptoms of the illness. What they don’t know is the extent to which the various abnormalities are genetically inherited or caused by some early environmental factor (obstetric complications, for example), or by an interaction between the two. It is also unclear how these factors then contribute to a process that might begin early in life, or much nearer in time to the onset of the illness.
Knowing the main causes of abnormal behaviour is very important to guide future treatment. If they are environmental or disease-related, practical steps can be taken to reduce their impact. Knowing which abnormalities are genetically determined, on the other hand, can help genetic studies narrow down their search for predisposing genes. Knowing which genes predispose someone to a disorder can help develop new and better treatments, as well as increase overall understanding of that disorder.
The Maudsley Bipolar Twin Study
Pairs of identical and non-identical twins aged 16 to 60 are participating in this ongoing study, which started in 2003 and is partly funded by the IoP-based Psychiatry Research Trust and NARSAD (The Mental Health Research Association). Some 80 pairs of twins have taken part in the study so far: some participants have a diagnosis of bipolar disorder; others don’t.
About one in every 100 people will suffer from bipolar disorder: 75 per cent of bipolar patients experience their first episode before they are aged 25. Bipolar disorder is a severe form of mood disorder, during the course of which the person affected experiences both extremes of mood – low (depression) and high (mania). Psychotic symptoms – such as delusions and hallucinations – can occur in either depressed or manic states.
To find out more about bipolar disorder, visit www.mentalhealthcare.org.uk.
The research team hopes to find out more about the genetic and environmental causes and triggers of bipolar disorder. Living with bipolar disorder can make life extremely difficult, and it essential to increase understanding of the illness in order to develop better treatments.
Participants in the study are asked to complete questionnaires and neuropsychological tasks, take a zygosity test to establish whether they are identical or non-identical twins, and have an MRI brain scan. The neuropsychological tasks consist of answering questions and solving simple problems, or of completing simple tasks on a computer. These tasks give the research team information about different mental functions, such as attention and learning, abstract thinking and the ability to solve problems. The MRI scans give detailed images of the structure of the brain to allow researchers to look for differences in those with bipolar disorder and those without; others give images which indicate active regions of the brain while participants carry out different tasks.
The majority of tasks can be carried out in volunteers’ homes, though the MRI brain scan needs to be done at the Institute of Psychiatry. The research team will arrange and pay for travel and, if necessary, accommodation costs in London, and make a small payment to thank participants for their time, but this is liable to income tax. Even if you can’t travel to London, the research team would still like to hear from you: your contribution is helpful, even if you can’t complete all the tasks.
Find out more about volunteering by downloading
The Maudsley Bipolar Twin Study: information for volunteers
If you’re interested in taking part in The Maudsley Bipolar Twin Study,
contact Anna Georgiades 020 7848 0023,
anna.georgiades@iop.kcl.ac.uk;or Eugenia Kravariti, 020 7848 0331.
We are Also looking for HEALTHY SIBLING PAIRS.
Tel: +44 (0) 20 7848 0023 or e-mail: Anna.Georgiades@iop.kcl.ac.uk
Who’s Who in the Bipolar Twin Study
Dr Timothea Toulopolou, Lecturer
Dr. Marco Picchioni, Clinical Lecturer
Madiha Shaikh, PhD Student and Research Worker
Sheena Owens, PhD Student and Research Worker
Sheena Waters-Metenier, Research Worker
Anna Georgiades, PhD Student
Fergus Kane, Research Worker
Dr Eugenia Kravariti, Lecturer
Dr Anirban Dutt, Clinical Research Worker
Dr Elvira Bramon, Senior Lecturer
Dr John Powell, Senior Lecturer
Professor Robin Murray, Professor of Psychiatry
The Maudsley Schizophrenia Twin Study
Twins have participated in research about schizophrenia at the IoP for more than 50 years and contributed to some landmark research about this illness. The most recent phase of the work has involved more than 200 twins from all over the British Isles and aims to explore the genetic and environmental causes of schizophrenia. The research team is also investigating the causes of some of the symptoms of the illness, such as hearing voices.
Everyone hears their own voices in their head – when they read, when they think, when they write, for example. Researchers are trying to find out how people with schizophrenia get confused and appear to misinterpret their own thoughts as someone else’s.
They are using a model based on a theory called Self-Monitoring which suggests that the brain recognises a self-generated thought because it has a built in ‘monitor’ that checks the origin of all nerve impulses to determine whether they began inside or outside the brain. The theory suggests that to correctly identify the origin of an impulse, this monitor needs to be working perfectly. If not, and an impulse is picked up without an indication that it began inside the person, the ‘logical’ assumption the brain makes is to assume it began outside. They are investigating this theory using MRI brain scanning to understand more about what processing steps the brain goes through when determining the origin of a voice, thought or impulse.
The Maudsley Schizophrenia Twin Study has been funded by the Wellcome Turst, NARSAD (The Mental Health Research Association) and the Stanley Medical Research Institute.
As well as having a brain scan, participants in The Maudsley Schizophrenia Twin Study are asked to fill in a series of questionnaires that can be completed at home, and have an evoked potential (EP) (or event related potential) recording of brain electrical activity to help researchers understand more about brain function. An EP is based on a test called an EEG (Electroencephalogram), carried out routinely in most hospitals. It is similar to an ECG test, but the leads are attached to the head, instead of the chest. Participants are also asked to carry out neuropsychological tasks, which consist of answering questions, solving problems or completing simple tasks on the computer.
The research team is looking for volunteer twins who have schizophrenia, where either or both of the pair are ill, and for twins who don’t have the illness, to participate in the ongoing Maudsley Schizophrenia Twin Study.
The team will arrange and pay for travel to the IoP and any accommodation costs and make a small payment to thank you for your time. Even if you can’t travel to London, you could still contribute and the team would like to hear from you.
If you’re interested in helping to find out more about schizophrenia, contact Madiha Shaikh, 020 7848 0541, madiha.shaikh@iop.kcl.ac.uk; Marco Picchioni, 020 7848 0049/0355, marco.picchioni@iop.kcl.ac.uk; or Timothea Toulopoulou, 020 7848 0061, timothea.toulopoulou@iop.kcl.ac.uk.
To find out more about schizophrenia, visit www.mentalhealthcare.org.uk/
Findings and publications from the Maudsley Schizophrenia Twin Study to date:
Hall MH, Rijsdijk F, Picchioni M, Schulze K, Ettinger U, Toulopoulou T, Murray RM, Sham P. Substantial shared genetic influences on schizophrenia and event-related potentials. American Journal of Psychiatry 2007; 164: 804-812.
Ettinger U, Picchioni M, Landau S, Matsumoto K, van Haren N, Marshall N, Hall M-H, Schulze K, Toulopoulou T, Davies N, Ribchester T, Murray RM. Magnetic Resonance Imaging of the Thalamus and Adhesio Interthalamica in Twins with Schizophrenia. Archives of General Psychiatry 2007; 64: 401-409.
Hall MH, Schultze K, Rijsdijk F, Picchioni M, Ettinger U, Bramon E, Freedman R, Murray R, Sham P. Heritability and reliability of P300, P50 and duration mismatch negativity. Behaviour Genetics 2006; 36: 845-857.
Ettinger U, Picchioni M, Hall M, Schulze K, Toulopoulou T, Landau S, Crawford TJ, Murray RM. Antisaccade Performance in Monozygotic Twins Discordant for Schizophrenia: The Maudsley Twin Study. American Journal of Psychiatry 2006; 163: 543-545.
Picchioni MM, Toulopoulou T, Landau S., Davies N, Ribchester T, Murray RM. Neurological Abnormalities in Schizophrenic Twins. Biological Psychiatry 2006; 59: 341-348.
Rijsdijk FV, van Haren NEM, Picchioni MM, McDonald C, Toulopoulou T, Hulshoff Pol HE, Kahn RS, Murray R, Sham PC. Brain MRI Abnormalities in Schizophrenia: Same Genes or Same Environment? Psychological Medicine 2005; 35: 1399-1409.
van Haren NEM, Picchioni MM, McDonald C, Marshall N, Davis N, Ribchester T, Hulshoff Pol HE, Sham P, Kahn RS, Murray RM. A Controlled Study of Monozygotic Twins Concordant and Discordant for Schizophrenia. Biological Psychiatry 2004; 56(6): 454-61.
Schnack HG, Neeltje EM van Haren, Hilleke E, Hulshoff Pol HE, Picchioni M, Weisbrod M, Sauer H, Cannon T, Huttenen M, Khan RS. Reliability of Brain Volumes from Multi-centre MRI acquisition: a calibration study. Human Brain Mapping 2004; 4: 312-20.
Picchioni M. Differences in fMRI and MRS in a monozygotic twin pair discordant for schizophrneia – invited comment. Acta Psychiatra Scandinavia 2003; 107(2): 157-158.
EUTwinsS (European Twin Study Network on Schizophrenia)
This is the largest international study of twins affected by schizophrenia in the world and involves a collaboration between nine mental health research centres in six European countries: Germany, the UK, The Netherlands, Spain, Hungary and Switzerland. The UK team is based in The Maudsley Schizophrenia Twin Study in the Section of General Psychiatry and has already been studying twins to find out more about schizophrenia.
Funded by the European Union through Marie Curie Actions Research Training Network, the project’s remit is to both advance understanding of schizophrenia and to promote learning, teaching and mobility of researchers across Europe. EUTwinsS started in 2006 and is funded until 2010.
The EUTwinsS consortium is a multidisciplinary network which will use neuroimaging, neurophysiology and neurocognitive methods as well as molecular genetics to study twins with schizophrenia.
Researchers will study brain structure and cognitive function and aim to identify and find out how specific genes predispose people to schizophrenia.
EUTwinsS will also offer researchers state-of-the-art training, at collaborating centres and on-line.
The UK research team is looking for volunteer twins who have schizophrenia, where either or both of the pair are ill, and for twins who don’t have the illness to participate in the ongoing EUTwinsS project. Volunteering to take part in the EUTwinsS project does not mean that you would have to travel outside the UK.
As well as having a brain scan, participants in the EUTwinsS project are asked to fill in a series of questionnaires that can be completed at home, and have an evoked potential (EP) (or event related potential) recording of brain electrical activity to help researchers understand more about brain function. An EP is based on a test called an EEG (Electroencephalogram), carried out routinely in most hospitals. It is similar to an ECG test, but the leads are attached to the head, instead of the chest. Participants are also asked to carry out neuropsychological tasks, which consist of answering questions, solving problems or completing simple tasks on the computer.
The research team will arrange and pay for travel to the IoP and any accommodation costs, and make a small payment to thank you for your time: this is liable to income tax. Even if you can’t travel to London, you could still contribute and the team would like to hear from you.
If you’re interested in taking part in the EUTwinsS project, contact Madiha Shaikh, 020 7848 0541, madiha.shaikh@iop.kcl.ac.uk; Marco Picchioni, 020 7848 0049/0355, marco.picchioni@iop.kcl.ac.uk; or Timothea Toulopoulou, 020 7848 0061, timothea.toulopoulou@iop.kcl.ac.uk.
To find out more about schizophrenia, visit www.mentalhealthcare.org.uk/