News in Science

Scans reveal key difference in mental disorders

Brain breakthrough Scans have revealed a critical difference in the way the brain processes emotions in people with two closely related mental disorders.

In a letter published recently in the prestigious journal Molecular Psychiatry, Australian researcher Professor Gin Malhi shows biological differences in the brain between people with bipolar disorder and those with borderline personality disorder.

Director of the CADE Clinic at the University of Sydney, Malhi says the findings have important implications for treatment as the two disorders are often misdiagnosed.

"Bipolar disorder and borderline personality disorder are difficult to distinguish because emotion dysregulation is a key feature of both," says Malhi.

"The key problem is we don't have biological markers for any psychiatric disorder," says Malhi. "Diagnosis is dependent on symptoms and grouping of symptoms into syndromes."

These groupings are outlined in the Diagnostic and Statistical Manual of Mental Disorders with the latest and fifth edition, DSM5, to be released in May.

Malhi says the two disorders have traditionally been separated as Axis 1 and Axis 2 disorders within the manual.

Axis 2 disorders are personality based and therefore long-term disorders, while Axis 1 can come and go and can theoretically be cured," says Malhi.

Wrong treatment

Critically the treatments for the two disorders are quite distinct with those with bipolar treated primarily with medication, while borderline personality disorder is treated psychotherapeutically.

"If patients are misdiagnosed they are not getting the treatment they need," says Malhi.

The study involved imaging the brains of 16 non-depressed bipolar patients, 13 borderline personality disorder patients and 14 controls with no mental illness.

While the brain was being scanned they undertook a task known as the emotional Stroop that makes participants work and engage key networks within the brain.

"The task causes a lot of conflict and if you have to do it repeatedly it is exceptionally taxing," he says.

Malhi says he adapted this task to focus on emotional responses and looked at how the regulatory circuits in the brain responded.

He says the study showed a clear difference in the biology of the two mental disorders.

"Patients with bipolar are able to function quite normally when well," says Malhi.

"[But] they have to do it at the cost of extra effort in the brain."

He likened it to the extra energy a short person would use when trying to keep pace walking with a taller person.

"The dorsomedial prefrontal cortex is critical and this is the area that they are drawing on," says Malhi.

Borderline personality disorder patients show heightened activity in the amygdala, which is the area related to our fear response.

"It is the key node in the lower part of the brain that co-ordinates emotional understanding … and they are not able to regulate it," he says.

Replication needed

Malhi says the results are "significant" however he stresses the study needs replicating with a larger cohort.

He says the finding has "huge" clinical implications and opens the way for better targeted diagnosis and therapy.

"It would be wonderful to put a patient in a scanner, look at their brain and inform our clinical judgments with biological information and direct our therapies accordingly," says Malhi.

However he says the discipline is "still stuck in the previous century in the taxonomy of psychological disorders".

"For the first time in the past two decades we have the technology to see the brain functioning [but] these insights and understanding have to be translated into clinical practice."