Diagnosing depression isn’t a simple matter of brain scanning

    4 August 2016

    Scientists at Japan’s Centre for Life Science Technology have developed a new, non-invasive brain scanning technique that they say can diagnose depression.

    The PET (Positron Emission Tomography) scan obtains images of the dentate gyrus, a neurogenic region of the brain (where neural stem cells give rise to new neurons) known to be particularly affected by depression.

    Currently the process of neurogenesis is difficult to monitor non-invasively. It is possible using an MRI scanner, but the process involves an injection into the brain fluid, making it invasive and difficult to perform.

    Yosky Kataoka, the study’s lead author, said: ‘This is a very interesting finding, because it has been a longtime dream to find a non-invasive test that can give objective evidence of depression and simultaneously show whether drugs are working in a given patient.’

    ‘We have shown that it is possible, at least in experimental animals, to use PET to show the presence of depression and the effectiveness of drugs. Since it is known that these same brain regions are involved in depression in the human brain, we would like to try this technique in the clinic and see whether it turns out to be effective in humans as well.’

    Only a few hospitals in the UK have PET scanners, so the technique is unlikely to be widely used even if further trials prove effective.

    Instant analysis

    This study certainly provides some interesting ideas and information, however it is difficult to establish how this could be applied clinically at such an early stage. Firstly, the study was carried out on rats who had been injected with corticosterone to trigger depression, and then treated with antidepressants, so already we are aware that things may be very different in humans with depression, and far more research would need to be done in order to establish whether this investigation method would be effective in humans. Secondly, depression is such a multifaceted illness, affected by not only the scientific disease process but also by psychological and environmental factors, which is what often makes it so difficult to diagnose and treat. It would certainly be helpful to have diagnostic tests to confirm diagnosis and treatment effects, but in reality the clinical presentation of the patient and their experience of the illness is paramount.