How is it that Lamotrigine, an antiepileptic, can help depression, a seemingly different disorder altogether? And why can Prozac, an antidepressant, help reduce anxiety? Or an antipsychotic for schizophrenia help depression? In other words, how is it that drugs for one type of major psychiatric disorder treat the symptoms of another type?
The root causes of psychiatric illnesses such as bipolar disorder, major depression, schizophrenia, autism and ADHD are far from understood. Even so for more than 125 years, clinicians have based diagnosis on groups of symptoms observed in patients. Many psychiatrists have thought for a long time now that the current categories don’t really make sense, and that new categories should be based not on symptoms but on the underlying biology.
Moving in that direction more than 300 scientists at 80 research centers in 20 countries scientists have now found that the five psychiatric disorders mentioned above share a common genetic basis. The overlap of these disorders was highest between schizophrenia and bipolar; moderate for bipolar and depression and for ADHD and depression; and low between schizophrenia and autism.
These findings still leave much of the inherited genetic contribution to the disorders unexplained. And none of this accounts for the non-inherited genetic factors that go into determining what a person is like. However, they demonstrate that science is now moving toward understanding the molecular basis of psychiatric illness, which could provide insight into the biological pathways that may predispose someone to health or disease. All this could ultimately lead to new treatments.
Genetic inheritance does not mean our fate is carved in stone, i.e. that because we are wired in a particular way genetically our fate is sealed. This is because it has become increasingly clear over the last 10 years or so that environmental factors determine which of our genes are “turned on” and which are “turned off”. In the scientific literature this is often spoken of as which genes are “expressed” and which are not. Whether your genes are turned on or turned off matters just as much as much as which genes you have.
Two recent experiments, one involving people and the other mice, suggest that regular exercise improves memory. However, different types of exercise affect the brain differently.
In the 1990s scientists at the Salk Institute in La Jolla, Calif., discovered that exercise “bulks up” the brain. In groundbreaking experiments, they showed that mice given access to running wheels produced far more cells in an area of the brain controlling memory than animals that didn’t run. The exercised animals then performed better on memory tests. Since then, scientists have been working to understand precisely how, at a molecular level, exercise improves memory, as well as whether all types of exercise, including weight training, are beneficial.
In one recent study, published in The Journal of Aging Research, scientists recruited dozens of women ages 70 to 80 with mild cognitive impairment, which is a recognized risk factor for increasing dementia.
Earlier research had found that after weight training, older women with mild cognitive impairment improved their associative memory, or the ability to recall things in context — a stranger’s name and how you were introduced, for instance.
Now the scientists wanted to look at both other types of memory and at endurance exercise as well. So they randomly assigned their volunteers to six months of supervised exercise. Some of the women lifted weights twice a week. A second group walked briskly. And the third group, who acted as a control measure, skipped endurance exercise and instead stretched and toned.
At the start and end of the six months, the women completed tests of verbal and spatial memory, both of which deteriorate with age. This loss is even more noticeable with mild cognitive impairment. In this study, after six months, the women in the stretching toning group actually scored worse on the memory tests than they had at the start of the study.
But the women who had exercised, either by walking or weight training, performed better on almost all of the cognitive tests.
But there were differences. While both exercise groups improved almost equally on tests of spatial memory, the women who had walked showed greater gains in verbal memory than the women who had lifted weights. The authors concluded that endurance training and weight training might have different physiological effects within the brain and cause improvements in different types of memory.
That idea correlates well with the results of another recent study of exercise and memory, in which lab rats either ran on wheels or “lifted weights”. Specifically, the researchers taped weights to the animals’ tails and had them repeatedly climb little ladders to simulate resistance training.
After six weeks, the animals in both exercise groups scored better on memory tests than they had before they trained. Even more interesting is that scientists found the runners’ brains had increased levels of a protein known as BDNF, or brain-derived neurotrophic factor, which support existing neurons and encourages the creation of new brain cells. The rat weight-trainers’ brains, on the other hand, did not show increased levels of BDNF.
The tail trainers, however, had significantly higher levels of another protein, an insulin-like growth factor, than the runners did. This substance, too, promotes cell division and growth and probably helps fragile newborn neurons survive.
What all of this new research suggests is that it’s probably best to incorporate both aerobic and resistance training. It seems that each type of exercise selectively targets different aspects of cognition, probably by promoting the release of different proteins.
But whether you choose to focus solely on aerobic or resistance training, at least in terms of memory improvements, the differences in the effects of each type of exercise were subtle. However, the effects of exercise — any exercise — on overall cognitive function are profound. Regular exercise improves memory.