The Black Dogs Barks Loudest
I spent the better part of last week deep in the throes of a depressive episode. I’ve talked extensively about my struggles with the Black Dog on this blog and in my social media so this is nothing new to look most of you. Here I’d like to delve deeper into how I manage my depression with aerobic training and how it works.
The Neurological Basis for Depression
Neurotransmitters work at the synapse level of the brain and include serotonin, dopamine, epinephrine and norepinephrine - and many others - and affect everything from mood and sleep/wake patterns (serotonin) to blood pressure and heart rate (norepiphrine) to how we perceive “rewards” (dopamine). As someone with depression, the theory is that my serotonin levels are lower than normal, although a recent study has challenged this theory. Regardless of whether or not low serotonin levels cause depression, the neurotransmitters listed play a significant role in regulating mood.
Another avenue by which mood can be regulated is through brain-derived neurotropic factor (BDNF), which protects neurons from the damage caused by high levels of cortisol, a stress hormone. One effect of depression is a structural change in a part of the brain called the hippocampus, where learning and memory happens. One study estimated that a depressed person’s hippocampus is up to 15% smaller than a normal person’s hippocampus. BDNF protects the hippocampus from the damages of cortisol and can enable stronger connections between neurons.
So where does aerobic exercise fit into this equation?
Aerobic exercise (AE), specifically, training under 75% of max heart rate affects every neurological function that has been identified as a potential cause of depression and acts on all the same neurotransmitters as the class of anti-depressants known as SSRIs - selective serotonin reuptake inhibitors. AE stimulates the release of norepinephrine which immediately improves self-esteem and elicits an acute dopamine release. More interestingly, long-term AE actually increases the amount of dopamine the brain stores. AE’s effects on serotonin are slightly different, but no less important: it helps decrease cortisol levels during stressful situations. And these are just the impacts on neurotransmitters…
The really interesting impacts are on BDNF. AE can actually boost the amount BDNF the brain produces IN EXCESS OF amounts produced by the use of anti-depressants, protecting the all-important hippocampus from the destructive effects of chronic stress and cortisol.
Indirect Effects
My colleague Dan Howells champions aerobic work with athletes and for good reason. He always talks about the “indirect effects,” or the intangibles we can’t quantify in a training setting. The management of depression using aerobic training is the quintessential indirect effect. If you are not impacted by depression directly, you know someone who is and can definitely use aerobic training.