(CNN) -- You think you may be suffering from depression and visit a psychiatrist to have your condition assessed.
The research was based on Duke Nukem, a popular video game
Rather than being given a form to complete, or asked a series of probing questions about dreams and your relationship with your mother, you are instead kitted out with a rocket launcher, ray gun, jet-pack and night vision goggles and sent forth to do battle against marauding aliens, the level of skill you bring to your mission determining the severity of your illness.
It sounds like a slightly surreal, bad-taste comedy sketch. According to a team at the U.S. National Institute of Mental Health (NIMH) in Bethesda, Maryland, however, a video-game based on the above scenario could provide crucial clues not only in diagnosing depression, but also in gauging the severity of that depression.
The game in question is Duke Nukem, a hugely popular virtual reality adventure in which the eponymous Duke -- a muscular, crop-haired, womanizing macho-man in the Arnold Schwarzenegger mold -- defends the earth, and in particular its female inhabitants, against an unpleasant array of aliens, mutants and other physically malformed aggressors.
Battle is joined in a variety of virtual environments, ranging from urban cityscapes to military bases and space stations, with the Duke navigating his way around these environments shooting, bombing, incinerating, stabbing, shrinking, freezing and otherwise terminating (with extreme prejudice) his hapless opponents.
It is the navigational, as opposed to martial elements of the game that have attracted the interest of the NIMH team.
A number of studies into depression have indicated that the condition could be linked to shrinkage or dysfunction of the hippocampus, the part of the brain concerned with memory and spatial awareness.
By using a virtual town based on scenes from Duke Nukem, and asking volunteers to navigate their way to various landmarks around that town in a set period of time -- albeit minus the weaponry and aliens -- the NIMH team, led by Neda Gould, have been able to assess spatial awareness and memory.
Those volunteers suffering from depression showed a distinct impairment of such mental functions, providing Gould and her team with a yardstick against which to measure the severity of their depression (the most chronically depressed volunteers posted the worst results in the trial).
"Neuropsychological testing has long established the presence of memory deficits in patients with unipolar depression, and, more recently, in those suffering from bipolar depression," writes Gould in an article on her findings in the American Journal of Psychiatry.
"Traditionally tasks assessing spatial memory require individuals to remember the position of items in an array.
"Because of their multi-faceted nature, navigational tasks based on virtual reality may provide a more consistent, sensitive measure of spatial ability and are more likely to require hippocampal involvement, thereby increasing their sensitivity to the impact of depression on this cognitive domain."
Unlike overtly physical illnesses such as diabetes, which can be diagnosed and assessed with a simple test, there is no such catch-all technique to quantify the severity of a mental condition such as depression.
"Depression is extremely complex," explains London-based psychoanalyst Jean Allen, "And can be very hard to diagnose and evaluate.
"It manifests itself in a variety of different ways for a variety of different people. At one end of the scale you have got those who suffer only mildly and whose lives aren't too badly affected; at the other you have chronic clinical depression that, at its worst, can tip into full-scale psychosis.
"Measuring exactly where someone is on that continuum, or indeed if they are on it at all, is very hard."
The Diagnostic and Statistical Manual of Mental Disorders -- the "bible" for mental health professionals - lays out categories of mental disorder, and various criteria for diagnosing and assessing those disorders.
Likewise numerous depression rating scales such as the Beck Depression Inventory, the Montgomery-Asberg Depression Rating Scale, the Hamilton Depression Rating Scale and the Inventory of Depressive Symptomatology have been developed to try to quantify and measure the severity of mental illness.
It remains an imprecise science, however, and one that relies on a gradual piecing together of information through question and answer rather than any clear cut, one-off diagnostic test.
"There are a variety of questionnaires you can use to help assess someone's condition," says Jean Allen, "But from a psychoanalyst's point of view they are not really very accurate."
The virtual reality navigation test could help to fill this gap.
The use of such virtual games to assess mental condition is not in itself new. A team from the Hebrew University of Jerusalem has used navigation through a virtual reality maze to help in the diagnosis of schizophrenia, while another study from the U.S. National Institute on Aging, Baltimore, has employed a similar system to quantify the mental deterioration caused by old age.
The NIMH experiment, however, is the first of its kind to apply such technology to the problems of depression.
The study combined 30 male and female volunteers from the in-patient and out-patient psychiatric units at NIMH, ages ranging of 21-65, with 19 healthy "control" volunteers. People displaying a "high expertise" in video games were excluded.
The volunteers were allowed to familiarize themselves with a virtual reality town such as that used in Duke Nukem, before being given 20 minutes to navigate their way around that town locating various landmarks.
The results proved extremely instructive. The healthy control group were able to find their way to significantly more locations (an average of 3.8) than those suffering from depression (an average of 2.4).
Within the latter group there emerged a clear correlation between severity of depression and navigational ability, with those suffering from the most acute depression displaying the least ability to find their way around the virtual town.
"Our results suggest that spatial memory performance on a virtual reality navigation task may represent a quantifiable measure to assess possible hippocampal deficits in patients with depression," concludes Gould's article in the American Journal of Psychiatry.
While the study does not provide a cut-and-dry means for actually diagnosing depression, it certainly offers the possibility of a new and more accurate yardstick for measuring the level of depression.
"As a purely diagnostic tool I think its effectiveness is limited," says Jean Allen. "My spatial awareness is appalling, but I am not clinically depressed.
"As a test for severity of clinical depression, however, I think it could have a huge and exciting role to play."
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