For the first time, a simple test which measures people's response to a sudden loud noise can distinguish between early and later onset schizophrenia. These findings from Dr Tonmoy Sharma's group from the Institute of Psychiatry, published in the June issue of the Archives of General Psychiatry, could ultimately lead to radical changes in the treatment of schizophrenia, a condition that affects 1 in 100 people in the UK.
Schizophrenia usually develops in late adolescence (over the age of 19) but people with a family history tend to develop the condition at an earlier age. It is not known why or whether this illness is biologically different from later onset schizophrenia. In addition, people who develop the illness at an earlier age have a worse outcome -- they often have more problems relating to other people, finding a job or living independently.
Until now, there has been no simple way of diagnosing schizophrenia. Psychiatrists use of range of symptoms such as hallucinations, delusions and problems in cognition -- memory, attention, decision-making -- to pinpoint schizophrenia and there are currently no objective measures to distinguish between early onset and later onset forms of the condition. What is exciting about the new approach is that it uses an objective biological sign -- people's startle response to a loud noise.
The Prepulse Inhibition (or PPI) test, takes just over 20 minutes and measures the mind's ability to filter (or process) information. Information processing is fundamental to helping our brain work efficiently and unlike classic psychological tests, it is pre-conscious, therefore does not require motivation from study participants and can be seen in animals as well as humans.
When we hear a sudden noise or are unexpectedly startled, the body responds to this stimulus, for example by blinking. If the noise is preceded a fraction of second before by a quieter noise, our response to the loud noise is less pronounced. This is an indication of how well the mind can filter information. By simply playing a series of noises, some of them preceded by a quieter noise, the research team was able to measure the degree of PPI by the way the study participants blinked in response to the noises.
PPI can be altered with drug treatment or by changing the environment; for example, leaving rats in social isolation disrupts their PPI. It is disrupted in schizophrenia but recent studies from Dr Sharma's group have shown it can be recovered with the use of newer antipsychotic drugs. In the current study, information processing deficits (PPI scores) in early onset schizophrenia were shown to be more severe and less amenable to antipsychotics. The implications from the research findings suggest that people with early onset schizophrenia may not respond to current treatments with typical or atypical antipsychotics and indicate that this group may need a different treatment approach.
In line with other brain diseases, researchers are hopeful that this step could allow further developments in schizophrenia to occur; for example, distinguishing an early onset form of Alzheimer's disease allowed researchers to find the APO-E gene mutations and to identify people at risk of developing the illness. Dr Tonmoy Sharma, the principal investigator of the study, hopes that identifying biological characteristics of early onset schizophrenia may do the same thing; ' By finding subtypes of the illness, we make our task possible -- identifying biological markers of schizophrenia will become like looking for a needle in a single haystack rather than searching for that needle in the entire field'.
1. One person in 100 has schizophrenia
2. Psychiatrists have long believed schizophrenia may be a collection of several diseases. To be able to distinguish between these diseases would help to gain greater understanding of the illness and in the development of more specific treatments.
3. Currently the mainstay treatment for schizophrenia is the use of antipsychotic drugs. This involves a stressful wait and see period in order to determine whether the drug is effective.
4. Useful references: - Kumari V, Soni W, Mathew VM, Sharma T. Prepulse inhibition of the startle response in men with schizophrenia: effects of age of onset of illness, symptoms, and medication. Arch Gen Psychiatry. 2000 Jun;57(6):609-14. - Kumari V, Soni W, Sharma T. Normalization of information processing deficits in schizophrenia with clozapine. Am J Psychiatry. 1999 Jul;156(7):1046-51.
5. Further background on PPI and schizophrenia is available. For all further information on this study or work in the Section of Cognitive Psychopharmacology, please contact Dr T Sharma (44-4101-47555).
NOTE TO EDITORS: The Institute of Psychiatry is based at the Maudsley Hospital and is part of King's College, London, UK.
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