Your Brain on Exercise: New Science of Mental Health and Why it Matters
Let’s talk about mental health. Recently it was reported that 1 in 3 college freshman are reporting symptoms consistent with a diagnosable mental health disorder, and 1 in 5 adults experience mental illness in a given year (1). While this recent headline focuses on college students, mental illness impacts all, and is especially consequential in later years, with the highest rate for suicide in women between ages 45 – 64, and for men, ages 75+ sees the highest rate, with ages 45 – 64 just behind, and is the group with the largest percentage increase (2).
Among the 44.7 million adults in 2016 with any mental illness, just 43.1% received mental health treatment.
Mental illness costs the U.S. economy $193.2 billion in lost earnings every year, and adults with severe mental illness die, on average, 25 years earlier than others, the majority of which are due to a treatable medical condition (3). Additionally, among the 44.7 million adults in 2016 with any mental illness, just 43.1% received mental health treatment (48.8% for women and 33.8% for men). For young adults, of any gender, age 18-25, just 35.1% received care. Across age and gender, the percentage is even lower for those whose race/ethnicity is Hispanic or Latino (31%), Black (29.3%), or Asian (21.6%), compared to 48.7% for those identifying as White (4).
What’s clear then, is that there is an enormous number, to the tune of 25 million people, who either cannot access quality mental health care because of cost, availability, or other limitation, or who, because of the stigma surrounding mental health treatment, do not seek care. This includes various forms of talk therapy, support groups, medications, and more. For these 25 million people, lifestyle interventions including, and certainly not limited to, exercise are an essential starting point for improving quality of life. For the rest of this article, we’ll dive into why and how exercise and physical activity can be an effective intervention in improving function and life outcomes for those with mental illness.
Most people generally understand that by exercising, they feel better, but it goes much deeper than that. In a meta-analysis recently published in the journal Depression and Anxiety, they looked at 11 studies with 455 adult patients with clinical depression, and found that with an average of 45 minutes of moderate-intensity aerobic exercise performed three times a week, over an average of 9 weeks that there was a significantly large overall anti-depressant effect (5). These outcomes even held when participants could do whatever form of exercise they preferred!
“Resistance exercise training significantly reduced anxiety in both healthy participants and those with a physical or mental illness, and the effect size of these reductions is comparable to that of frontline treatments such as medication and psychotherapy.” – Brett Gordon
So aerobic exercise helps, but what about lifting weights and other resistance training? A recent meta-analysis published in the journal Sports Medicine, across 16 studies with a total of 922 participants, sought to answer that question. Study author Brett Gordon reported that “RET (resistance exercise training) significantly reduced anxiety in both healthy participants and those with a physical or mental illness, and the effect size of these reductions is comparable to that of frontline treatments such as medication and psychotherapy… RET is a low-cost behavior with minimal risk and can be an effective tool to reduce anxiety for healthy and ill alike” (6).
Additionally, many antipsychotic medications, particularly atypical antipsychotic medications, are known to lead to weight gain. Consequentially, those with schizophrenia have an expressed need for exercise interventions, and generally respond very well, with improvements in weight control, fitness level, ability to tolerate exercise, blood pressure, and energy levels! These improvements have been seen with as little as 30 minutes of brisk walking 3x per week, and could be done all at once, or split into 10-minute increments (7).
“Great, exercise helps, but how and why?” Funny you should ask, as an article from the Journal of Clinical Psychiatry seeks to answer just that! They propose that exercise induces an increase in blood circulation to the brain, and by influencing the HPA (Hypothalamic-Pituitary-Adrenal) Axis. This works to improve the physiological response to stress and also likely is boosted by signals sent to other regions of the brain that control several factors, including mood and motivation (limbic system and hippocampus), fear response (amygdala), and memory formation (hippocampus) (7).
On the cutting edge of understanding mental health and the role of exercise lies systemic inflammation, and in particular, a molecule called kynurenine. Systemic inflammation has been shown to be a biomarker for, and possibly influence the onset of, depression and other mental illnesses (8). During conditions of high inflammation, the essential amino acid tryptophan (yes, the one people talk about when you eat a large portion of turkey, which is more of a myth with a hint of truth, but that’s for another day) is broken down into a molecule called kynurenine, instead of it’s normal product, serotonin. This leads to a build-up of kynurenine in the brain, which is neurotoxic and is associated with depression and schizophrenia (9, 10).
So where does exercise come in? Exercise stimulates more significant expression of the enzyme KAT (Kynurenine Aminotransferase), converting kynurenine into kynurenic acid (Kyna), which has neuroprotective effects. In addition to the effect of exercise to reduce systemic inflammation, exercise also directly impacts the brain through this pathway and is an especially important intervention for stress-induced depression, which has a tight link to kynurenine build-up (11, 12).
Lastly, regular exercise over time builds up a resiliency to kynurenine toxicity and stress-induced depression by improving the ability of skeletal muscle to express the enzyme KAT. One study found that while those with a history of training did see greater KAT expression, it took only 3 weeks for sedentary adults to see improved KAT expression, among other benefits (13)!
Thank you for taking the time to read this article, I hope you’ve gotten some value from this, and if you did, pass it along! This is an important topic, and information can help people more than you know! Feel free to reach out with comments or questions, and if you’re in the Greater Boston area and want to get started exercising with a professional coach at your convenience, we’ll schedule you a complimentary workout!