Our ancestors reveal secrets about current rates of depression.
Posted Jul 22, 2009
Epidemiological research suggests that, even though times seemed to be tougher for our grandparents, our generation is up to 10 times more likely to experience depression than they were. Why, when our lives are seemingly easier than ever before in the history of our species, are depression rates higher than ever? What did our ancestors possess that we seem to be missing today? These questions prompted me to search for answers to this mental mystery. I found clues in the behavioral neuroscience literature, in the behavior and brains of the rodents in my laboratory, and in my personal experience with depressive symptoms following my mother’s death.
The convergence of evidence kept pointing to the value of directed movement toward life’s rewards, especially complex movement of the hands. Could the answer to this multi-billion dollar question (based on the amount of money spent on antidepressants each year) be so simple? It certainly seems that the key to preventing depression might have been in our hands all along. Our ancestors couldn’t order take-out-- they had to hunt or forage for food. Interestingly, a century ago doctors used to prescribe “knitting” to women overwrought with anxiety because they observed that this work calmed their patients’ nerves. And, most impressive for a neuroscientist, the brain devotes a disproportionately large area of the motor cortex to the movement of the hands. If “work” with the hands is an important aspect of human behavior, it is interesting to consider what would happen if such work or “effort driven rewards” were systematically removed from our lives. As scary as it seems, we’re currently conducting that experiment on ourselves. As “knowledge workers,” many of us work very long hours at the office with minimal movement of our bodies and hands beyond reflexively typing on our keyboards. Research suggests that our brains are minimally engaged in our physically deprived lives—leading to reduced pleasure, decreased perception of control over the stress in our lives, diminished persistence in tough times, and an inability to problem-solve when faced with new challenges. Do these symptoms sound familiar?
Putting the effort-driven reward idea to the test in the laboratory, my students and I designed a study in which one group of rats was trained to dig for froot loop rewards each day (worker rats) whereas a second group was given their froot loop rewards regardless of their effort (trust fund rats). After six weeks, each animal was presented with an unsolvable problem (unbeknownst to the rats) and the worker rats persisted for nearly twice as long as the trust fund rats. The “effort-driven reward” training appeared to have immunized the worker rats against the “learned helplessness” often associated with depression. Also interesting, when we tested for the presence of a brain neuropeptide (Neuropeptide Y) that is associated with resilience, the worker rats had more than their trust fund counterparts.
As I’ve described in my recent book Lifting Depression: A neuroscientist’s hands-on approach to activating your brain’s healing power, I am now more convinced than ever that our drastically altered lifestyles have played a role in the rise of symptoms we associate with depression. This serious and debilitating disorder is by no means simple, just seems that we are sensitive to the removal of some of our brain’s simple pleasures…preparing a delicious dinner, planting a beautiful garden, carving a toy that delights a child or even knitting a scarf for a cantankerous co-worker. Thus, the hard work required for our ancestors’ survival might have been the best antidepressant of all!
Reference: Lambert, K.G. (2008). Depressingly Easy. Scientific American Mind (August/Sept).