Anxiety disorders are the most common mental disorders in New Zealand but their diagnosis is still based on symptom checklists with no biological markers to diagnose specific causes. A Dunedin research team hopes to change that.
Ask any two psychologists what anxiety is and you'll get three different answers, it is sometimes said.
But after 47 years of research into the workings of the mind, Prof Neil McNaughton, a behavioural neuroscientist at the University of Otago, has come up with his own definition of anxiety and what he believes is one of the first biomarkers associated with any mental disorder.
The 68-year-old, who has $1million from the Health Research Council to carry out further work, says both fear and anxiety are defensive reactions that have evolved to help us survive, but fear allows us to get away from danger and anxiety helps us carefully approach it.
Fear involves avoidance.
Anxiety involves an approach/avoidance conflict and is activated when a rat wants food at the end of a runway but can also smell a cat and so cautiously approaches, checking for risk.
Prof McNaughton found a brain rhythm in the hippocampus of rats that is involved in the control of such conflict and was reliably reduced by clinical anti-anxiety drugs.
He later recorded a similar drug-sensitive rhythm in humans from above the right frontal cortex during tests designed to mimic the goal-conflict aspect of anxiety.
Participants were told to click the mouse when an arrow appeared on a computer screen but not if they heard a beep.
The task difficulty varied so they were able to refrain from clicking 25%, 50% or 75% of the time.
When going and stopping were evenly balanced, they produced brain activity suggesting that they were activating the approach-avoidance systems equally in the brain and generating conflict.
In July, his team will be looking for anxious people who have not yet started treatment to undergo a slightly different version of the test.
The expectation is that those who score highly (whose reaction to conflict is hyperactive) will be defined as having a particular kind of anxiety and will be more likely to be successfully treated with anti-anxiety drugs whereas those who do not show such a response will be more likely to need other medications.
Prof McNaughton hopes the work will lead to better diagnosis and treatment, saying that at present our capacity to tell exactly what treatment to give what person is ''fairly poor''.
The work should lead to biomarkers being identified for not only other anxiety disorders but other mental disorders and, for the first time, should allow for multiple concurrent diagnoses.
Developing tests that look for a genuine disorder rather than just classifying people according to symptoms is an attempt to apply to psychiatry the approach taken in more general medicine and the ''equivalent of knowing people have got measles as opposed to just saying they've got a high temperature and spots of some kind'', he says.
''If we can get at the fundamental biology of these things, we're in a better position to understand them and potentially produce new therapies.''
