Exercise your way to happiness
On a daily basis, we all strive to some extent to be happy, to feel happy, or to make ourselves happier. No one enjoys feeling sad or depressed. Fortunately, we can add things to our daily regimen of activities to promote happiness. Some measures people take to increase happiness include thinking positive thoughts, eating satisfying foods, spending time with friends and family, or engaging in enjoyable activities. For some of us, exercise may be one of these activities. For others, exercise may be the last thing we would think of to promote happiness. No matter what your love of exercise may be, recent scientific evidence reveals that exercise is surefire way to make you happy.
When we look at older populations, we see that those who are in poor physical health (e.g., individuals suffering from heart disease, diabetes or arthritis) report lower levels of subjective wellbeing and have higher levels of depression (Steptoe et al., 2014). On the other hand, positive subjective wellbeing or happiness is a protective factor for health (Steptoe et al., 2014). The happier you are, the less likely you are to develop a chronic physical health condition and the more likely you are to live for a longer period of time. Of course, one of the best ways to stave off poor physical health is to exercise, and the authors of this review on wellbeing in aging claim that, “Of lifestyle factors, physical activity is probably the most important link between subjective wellbeing and health.” Additionally, a recent randomized controlled study conducted on 120 older adults revealed that only 8 weeks of aerobic exercise improved self-reported levels of happiness (Khazaee-Pool et al., 2015).
For some of us, happiness seems like an elusive phenomenon. Major depression is one of the most common mental health issues in the United States, with approximately 7% of our population experiencing at least one episode of major depression per year. Depression is characterized by low mood or loss of interest or pleasure as well as problems with sleeping, eating, energy, concentration and/or self-image for two weeks or more. Certain drugs known as selective-serotonin reuptake inhibitors (SSRIs) are prescribed for people with depression. Serotonin is a neurotransmitter that is produced in a small area of the brain called the raphe nuclei located in the brain stem. Though this area is small, the neurons or brain cells that carry serotonin spread to far reaching areas of the brain including areas involved in mood, memory, and conscious experience. SSRIs block the channels that allow serotonin to re-enter the neuron after its release from that same neuron, effectively causing serotonin to have a longer-lasting effect. Over time, these more immediate neurochemical changes lead to structural changes that are thought to underlie the effectiveness of the medication.
Not surprisingly, depression is associated with self-reported measures of low levels of exercise and high levels of sedentary behavior (Teychenne et al., 2010). Recent research using accelerometers has also revealed that depressed individuals move significantly less during the day than their healthy counterparts (https://pubmed.ncbi.nlm.nih.gov/22868056/), with these individuals spending the majority of their waking time sedentary (75% of the 12-hour day) (Helgadóttir et al., 2015). Based on these statistics, getting depressed patients moving may prove difficult, but it is necessary.
Just like treatment with SSRIs, engagement in physical activity decreases levels of depression (Craft, 2012). One study randomly assigned 202 individuals with major depressive disorder to one of four test conditions for four months: a supervised aerobic exercise group, a home-based aerobic exercise group, an SSRI group, or a placebo pill group (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702700/). They found that both aerobic exercise interventions were equally effective as the SSRI intervention and more effective than the placebo pill intervention at achieving depression remission (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702700/). This is one example of several randomized controlled trials that have examined the effects of exercise on depression. Systematic reviews of this literature have shown that aerobic exercise interventions are similarly effective to the psychotherapeutic and pharmacotherapeutic treatment of depression, and that a combination of these treatments is better than any singular treatment (https://pubmed.ncbi.nlm.nih.gov/19306383/ ; https://pubmed.ncbi.nlm.nih.gov/24026850/).
Perhaps not surprisingly, as SSRIs and exercise cause similar antidepressant effects, they also cause similar chemical and structural changes in the brain. It is still unclear exactly which of these changes are causing the antidepressant effects, but the literature points to a few promising pieces of evidence. For one, both exercise and SSRIs increase serotonin levels in the synaptic cleft or the area in between neurons. Additionally, both exercise and SSRIs increase levels of brain-derived neurotrophic factor (BDNF), a neurochemical that acts as a fertilizer for the brain. Finally, both of these treatments cause neurogenesis or the growth of new neurons in the hippocampus, an area of the brain involved in learning and memory. More research is needed to understand exactly what brain changes occur to cause the antidepressant effects of both exercise and SSRIs.
In conclusion, you can exercise yourself to a happier you. Whether you just feel sad or suffer from the serious medical condition of depression, exercise can be used as a way to improve your mood. Though this basic information is known, future research is needed to understand the best exercise prescription. What is the best type of exercise and what dose of it is needed to serve as an optimal treatment for depression? Finally, research focusing on the mechanistic similarities between exercise and SSRIs will help us to understand exactly why these two disparate things serve to make us happier.
References:
Aan Het Rot M, Collins KA, Fitterling HL (2009). Physical exercise and depression. Mount Sinai Journal of Medicine, 76(2): 204-214.
Blumenthal JA, Babyak MA, Doraiswamy PM, Watkins L, Hoffman BM, Barbour KA, Herman S, Craighead WE, Brosse AL, Waugh R, Hinderliter A, Sherwood A (2007). Exercise and pharmacotherapy in the treatment of major depressive disorder. Psychosomatic Medicine, 69(7): 587-596.
Burton C, McKinstry B, Szentagotai Tătar A, Serrano-Bianco A, Pagliari C, Wolters M (2013). Activity monitoring in patients with depression: a systematic review. Journal of Affective Disorders, 145(1): 21-28.
Cooney GM Dwan K, Greig CA, Lawlor DA, Rimer J, Waugh FR, McMurdo M, Mead GE (2013). Exercise for depression. Cochrane Database of Systematic Reviews, 9:CD004366.
