Mood swings on wings

style="float: right; margin-bottom: 10px; font-weight: 600;"Sun 26th May, 2013

Have you got a deadline coming up soon? Does it make you feel anxious, sleepless and stressed out? Some of us respond to tight deadlines by burning the midnight oil and getting the work done, but others simply give up, crushed with a feeling of helplessness that no matter how much effort one puts in, it is going to make no difference. It turns out that we are not alone. Scientists show that even pesky fruit flies (Drosophila melanogaster) exhibit similar behavior when faced with a difficult situation. New research published in Current Biology, and led by Dr Martin Heisenberg from the Rudolf Virchow Center in Wurzburg, uses fruit flies to investigate behavioral responses under trying circumstances. This work might lead to a better understanding of how to cope with mood swings and depression on the basis of fly behavior.

To study how fruit flies react to stressful situations, Dr Heisenberg's team exposed two groups of flies to heat, which is known to cause 'stress' in flies (and they therefore try to avoid it). One group of flies had control over the stress stimulus ('master' group) and the other did not ('control' group). In the master group, when the flies stayed idle the heat turned on, and when they became active it turned off. As these flies were rewarded for their active behavior, they learned to become more active to avoid the heat. On the other hand, the control group received similar amounts of heat exposure irrespective of their activity. These flies become inactive and sluggish, similarly to a condition experienced by many animals called "learned helplessness", which is induced by uncontrollable stressful events. Because of its similarities to human depression, "learned helplessness" in mammals is considered an experimental model for this mental illness. Could fruit flies become an animal model of human depression?

Dr. Heisenberg says this study "is not a model of a disease but the animal model of a human behavioral (mental) state that can turn pathological." He concludes that this is just the beginning. In the future, Dr. Heisenberg team will be exploring questions such as "How long does the depression-like state last? Can it be transferred to a different environment? Where in the brain is depression generated? " he adds.

Depression is a mental disorder that affects 5% of the total world population, corresponding to about 350 million people. Given the current nature of stressful lives that we lead, such as pressure in the workplace for instance, depression tends to affect individuals of all ages. In extreme cases, depression can lead to suicide. Alarmingly, according to a World health Organization (WHO) report, despite the prevalence of effective treatments for depression, fewer than half the affected individuals actually receive treatments. While this could be attributed to various reasons such as affordability, timely and accurate detection of the disorder and lack of trained physicians who can treat the illness, social stigma is the worst culprit. Due to a global rise of mental health disorders, the WHO has called for a concerted effort in diagnosing and treating depression among all the countries. As a result, studies like this one are very critical in not just helping medical research and improving the effectiveness of the cure, but also in creating a greater public awareness about the disorder.

Another interesting finding of Dr. Heisenberg's work is also that female flies have a stronger response to uncontrollable stress than males- they become even more irresponsive and lethargic in the presence of heat. Correlation studies have suggested that women are more prone to some mood and anxiety disorders than men. While this can be construed as an increased inclination of the female gender towards depression, it could be speculated that this tendency could be chalked up to "female intuition". Evolutionary theory suggests that female response to uncontrollable stress situations is geared towards conservation of energy for survival and procreation. On the other hand, the natural male response to stress is to make attempts to escape the difficult situation unmindful of all the energy spent in doing so. Perhaps not surprisingly, these very different responses to stress in males and females, fruit flies included, confirms the adage - Men are from Mars and Women are from Venus.

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