Using neuroimaging to differentiate between Bipolar Disorder and Borderline Personality Disorder

Bipolar Disorder (BD) and Borderline Personality Disorder (BPD) are often confused and misdiagnosed. Both disorders involve dysregulation of emotional responses as key diagnostic criteria. BD is a mental illness involving a set of significant 'mood swings'. The most common form of Bipolar involves 'highs' (or mania) and 'lows' (depression). BPD is a type of personality disorder, or a set of long-standing traits and behaviours associated with significant distress or disability. A key feature of BPD is affective liability, meaning that people with BPD have difficulty stabilising their moods and therefore can demonstrate erratic mood swings. They are also prone to depression. More information about both disorders can be found on the website of the Black Dog Institute.

As it is personality based BDP tends to be a long-term disorder, whereas BD can come and go and with the right treatment can be cured or well managed. Appropriate treatment and management requires proper diagnosis. Unfortunately until now there have been no biological markers for psychiatric disorders.

However, some promising new research has found that there may be a way to differentiate between BD and BPD at a biological level. Professor Gin Malhi from the Sydney University has found biological differences in the brains between people with the two conditions. Professor Malhi and colleagues scanned the brains of people with BD (who were not depressed at the time of the study), BPD and controls with no mental illness while they undertook a task that focuses on emotional responses and is cognitively taxing (the emotional Stroop task). They found a significant difference in the response of the emotional circuits in the brain of the two patient groups and between the patients and controls during the task.

Individuals with BP drew more on the dorsomedial prefrontal cortex of the brain, whilst people with BPD showed heightened activity in the amygdala, a lower level part of the brain which coordinates emotional responses and processes negative emotions such as fear. Professor Malhi reported that people with BPD were not able to regulate this "key node in the lower part of the brain that co-ordinates emotional understanding". In contrast, people with BP were able to function quite normally when well, and just needed to expend more effort in the brain than controls.

While the results are very promising, Prfessor Malhi stresses the need for replication of the study.

He concluded: "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."