Here in Toronto, the spring days are getting warmer. After another long and cold winter, we’re finally able to go outside without covering ourselves in obscene amounts of clothing. People are outside walking, running, biking and playing tennis. People also seem to be in better spirits.
If asked why people seem to be happier, most of those questioned would probably say the weather is responsible. But with better weather, more people are physically active, and numerous studies have reported that exercise improves mood, cognitive ability and brain function. The evidence is compelling, and psychiatry is beginning to take interest in the beneficial effects of exercise on disorders such as depression, anxiety and ADHD (see the book Spark: the Revolutionary New Science of Exercise and the Brain by Harvard psychiatrist John Ratey). This is an exciting area of research that I have been carefully following ever since I co-authored a paper on exercise to treat bipolar disorder.
The reason this research is so exciting is that we all know that exercise helps stave off diseases like cardiovascular disease, diabetes and obesity. If we accept that exercise can prevent and/or treat psychiatric disorders too, we can view exercise as an all-in-one solution to health problems of both the body and the mind.
A couple of studies on the effects of exercise on cognition and the brain have made news headlines this year. One study, conducted at the University of British Columbia, found that resistance training in elderly women resulted in significantly improved performance on tasks that involve executive cognitive function. Another study by a group in Germany found that exercise (stationary cycling) resulted in increased brain volume in the hippocampus, a structure involved in learning and memory, in patients diagnosed with schizophrenia (healthy control subjects who exercised also had increased hippocampal volume). It is interesting to note that these studies examined different forms of exercise – resistance training and aerobic training – yet both showed beneficial effects on brain health.
Now another study study, in press in Journal of Affective Disorders, has found that acute exercise (stationary cycling) increases blood levels of some cytokines in patients with major depressive disorder. Cytokines, substances that are secreted by the immune system, can function as pro-inflammatory or anti-inflammatory. They can also affect neurotransmission and can thus have significant effects on the brain. Some evidence suggests that pro-inflammatory cytokines are elevated in level in patients with depression.
Unfortunately this study only examined the immediate effect of exercise on cytokine levels, and it was actually found that some pro-inflammatory cytokines increased in blood levels. The results do not tell us much about the usefulness of using exercise to treat depression. However, they tell us that the long-term effects of exercise on cytokine levels should be studied to provide important insights on the mechanisms by which exercise exerts its effects on psychiatric disorders. Future studies should try to include severely depressed patients (this study only examined moderately depressed patients) and investigate the effects of different types of exercise.
Okay, enough rhetoric and time to go outside for a run... we’ll figure out the details later.