Patients with schizophrenia hardly represented in antipsychotic drug studies

No less than 80 per cent of patients who are prone to psychosis are left out of clinical studies on the effectiveness of antipsychotics. These drug studies apply strict exclusion criteria, which means that only the least ill patients participate, such as those who are susceptible to psychosis, but who do not suffer from addiction, physical illnesses or suicidal thoughts. It also appears that psychosis-prone patients who do suffer from such additional issues respond less well to antipsychotics than do patients who are less ill. These are the striking findings of international research led by Maastricht University (UM), published today in the medical journal JAMA Psychiatry.


For this study, the international research team used large-scale medical registries from Scandinavia dating back decades. In Sweden and Finland, meticulous records have been kept for many years detailing the clinical pictures of patients presenting to psychiatrists. The researchers compared data from tens of thousands of patients from these national registries – which focus on the patient in the consulting room – with the exclusion criteria that clinical studies of antipsychotics use when selecting subjects. Exclusion criteria include ‘liable to suicidal tendencies’, ‘suffering from physical illness’ and ‘addicted to drugs or medication’. Both the Swedish and Finnish registries showed that four out of five patients prone to psychosis who visit a psychiatrist are not eligible to participate in clinical trials of drugs to treat psychosis (antipsychotics).

Clinical studies

In addition, the researchers were able to deduce from the Scandinavian data that it is precisely the most complex cases that are more likely to develop serious illness when they receive antipsychotics than are psychosis-prone patients who do not suffer from addiction, physical illnesses or suicidal thoughts. Lead researcher and psychiatrist Jurjen Luykx therefore argues for greater inclusivity in large clinical trials, and for more specific studies among certain groups of patients who regularly appear in the consulting room, such as people suffering from both psychosis and addiction. ‘Our findings show that little is actually known about the best treatment for the most common psychosis-prone patients in the consulting room, namely those who are also prone to addiction, suicidal thoughts or physical illness. As a psychiatrist, I see many people who are vulnerable to psychosis and also suffer from these kinds of additional complaints. It is essential to know what treatment works well for these people, because we often see them in our consulting rooms. In future, we therefore need to be much more inclusive in scientific research into new drugs for people prone to psychosis.’

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