A Joyful Heart and the Immune System

The Hebrew word translated “medicine” (gehah) appears only here in the Old Testament. Most translators take it as “healing” or “cure,” so the line says something like “a glad heart does good healing.” In Hebrew idiom, “bones” often stand for a person’s whole frame and vigor, as in Proverbs 3:8 and 14:30. The proverb treats inner disposition and bodily health as connected. Its neighbors help us read it. Proverbs 17 is full of relationships: a dry morsel eaten in quiet is better than a feast with strife (17:1), and “a friend loves at all times” (17:17). Proverbs 18:14 completes the thought: “The spirit of a man can endure his sickness, But as for a broken spirit who can bear it?” In Solomon’s terms, joy is not a private mood. It is the state of a heart at peace with God and neighbor.

The viral-challenge studies. The most cited evidence comes from Sheldon Cohen and colleagues at Carnegie Mellon (Cohen, Doyle, Turner, Alper, & Skoner, 2003). They interviewed 334 healthy adults on several evenings over a few weeks to measure their typical positive emotional style (feeling happy, pleased, relaxed) and negative emotional style (anxious, hostile, depressed). Then every participant received nasal drops containing a rhinovirus and was kept in quarantine to see who developed an objectively verified cold. Higher positive emotional style went with lower risk of illness in a dose-response pattern. People in the lowest third for positive emotion were about 2.9 times as likely to develop a cold as those in the highest third, after controlling for prior antibodies, age, sex, education, race, body mass, and season. Happier people did have somewhat lower stress-hormone levels and better health habits, but those differences did not explain the gap.

The obvious objection is that “positive emotion” might just be a proxy for optimism, extraversion, or feeling healthy. So the team ran the study again with 193 new volunteers and two different viruses, a rhinovirus and influenza A (Cohen, Alper, Doyle, Treanor, & Turner, 2006). They also measured optimism, extraversion, mastery, self-esteem, purpose, and self-rated health. The result held, with an adjusted odds ratio of 2.9, independent of all of those traits. The design is unusually strong because everyone gets the same controlled exposure. It is still not a randomized experiment, though. No one was assigned to be joyful, so these studies show prediction, not proven cause.

What might be happening in the body. The field that studies this is called psychoneuroimmunology, and it describes two main “wires” from the brain to the immune system. The first is the HPA axis. The hypothalamus signals the pituitary gland, which signals the adrenal glands to release cortisol. Short bursts of cortisol calm inflammation. The second is the sympathetic nervous system, which releases adrenaline-like chemicals that reach immune tissues directly. When a cold virus infects the nose, the body’s tissue reaction, not the virus itself, produces most of the misery. Cells release cytokines, chemical messengers such as interleukin-6 (IL-6) that recruit inflammation and cause congestion and symptoms.

Two findings connect emotional style to those wires. First, in a sample of infected participants (n = 234 from 327 exposed), lower positive emotional style went with more nasal IL-6. Statistically controlling for IL-6 substantially weakened the link between emotion and illness, which suggests IL-6 is part of the pathway (Doyle, Gentile, & Cohen, 2006). Second, Cohen and colleagues showed that long-term threatening stress can make immune cells “deaf” to cortisol’s calming signal, a state called glucocorticoid receptor resistance. People with this resistance were more likely to develop colds and produced more inflammatory cytokines when infected (Cohen et al., 2012). In daily life, too, happiness tracks biology. Among 216 middle-aged London civil servants, the least happy fifth had about 32% higher cortisol output across a workday than the happiest fifth. They also showed a far larger stress-induced rise in fibrinogen, a clotting and inflammation protein (Steptoe, Wardle, & Marmot, 2005). Two small studies of young adults found that trait positive emotion, and awe in particular, predicted lower IL-6 (Stellar et al., 2015).

The broken spirit. The second half of the proverb is now one of the busier areas of psychiatry. Meta-analyses find that people with major depression have higher blood levels of the inflammatory cytokines IL-6 and TNF-alpha than non-depressed controls (Dowlati et al., 2010). Across community and clinical samples, depression goes with higher C-reactive protein, IL-1, and IL-6, though the effects are small (d about 0.15 to 0.35) and partly explained by body weight (Howren, Lamkin, & Suls, 2009). The traffic runs both ways. In a randomized experiment, healthy volunteers given a safe, low dose of bacterial endotoxin (which triggers a brief cytokine surge) became measurably more depressed in mood than those given placebo. Their ventral striatum, a reward hub, also responded less to anticipated rewards (Eisenberger et al., 2010; n = 39). Researchers think this “sickness behavior” (withdrawal, fatigue, loss of pleasure) evolved to help a wounded body rest. In modern life, social rejection and chronic threat can switch it on without any infection (Miller & Raison, 2016; Slavich & Irwin, 2014). “Dries up the bones” is not a bad description of what that state feels like.

Two honest notes keep us from forcing the fit. In the 2003 cold study, negative emotional style did not predict verified colds, though it did predict complaining of symptoms that had no objective basis. And across 35 prospective studies of initially healthy people, positive well-being predicted lower mortality (combined hazard ratio 0.82). That is meaningful but modest, and the authors found signs of publication bias (Chida & Steptoe, 2008). Pressman and Cohen’s (2005) major review adds a caution: intense, highly aroused bursts of positive emotion can briefly raise physiological strain. The calmer, everyday contentment the proverb seems to describe is what tracks with protection. The data fit the first half of the proverb more cleanly than a simple “sad people get sick” reading of the second half. That is a good reminder not to press a text and a study into perfect alignment.

Practice

Living it out

Five practices drawn from this passage. Each says how strong the research behind it is. What the labels mean.

1. 1

   Practice joy on purpose, together

   Joy in Proverbs 17 lives among friends, and the data agree. In Cohen’s hugging study (404 adults tracked for 14 evenings and then exposed to a cold virus), feeling supported protected against the rise in infection risk that came with frequent conflict. Daily hugs accounted for about a third of that protection, and among infected participants, more hugs predicted milder illness (Cohen et al., 2015). Make it concrete: greet your wife and kids with a real embrace, and hold your wife’s hand when bad news comes. In a partner study, a familiar partner’s hand (not a stranger’s) reduced threat-related brain activity in 110 adults (Coan et al., 2017).

   ModerateThese are prospective and lab studies, not trials showing that adding hugs prevents colds.
2. 2

   End each day with a short gratitude review

   Before bed, name three specific gifts from the day to God in prayer (“Rejoice always… in everything give thanks,” 1 Thess. 5:16 to 18). Randomized trials of gratitude exercises show real but small effects. A meta-analysis of 27 studies (n = 3,675) found g = -0.29 on depression and anxiety symptoms, smaller than active therapies (Cregg & Cheavens, 2021). Broader positive-psychology programs raise well-being modestly (d = 0.34) (Bolier et al., 2013).

   ModerateModerate for mood, weak or unknown for immunity. No trial has shown that gratitude journaling prevents infection.
3. 3

   Make room for awe in worship and creation

   Psalm 19 and Psalm 8 model stopping to wonder. Take a walk under the night sky, or sing a hymn and actually attend to the words. In two correlational studies, awe was the positive emotion most strongly linked to lower IL-6 (Stellar et al., 2015). Over 16 years among 74,534 nurses, attending services more than once a week predicted 33% lower mortality, with social support, lower depression, less smoking, and optimism partly explaining the link (Li et al., 2016).

   SuggestiveThese are correlational studies, and churchgoers differ in many ways.
4. 4

   Take a broken spirit seriously and get help

   “Who can bear” a broken spirit (Prov. 18:14) is a call to bear one another’s burdens (Gal. 6:2), not to “smile more.” If a brother has lost pleasure, energy, or hope for weeks, help him reach a pastor, doctor, or counselor. A meta-analysis of 56 randomized trials (n = 4,060) found that structured psychosocial treatments, especially cognitive behavioral therapy, improved immune markers, with about an 18% drop in harmful inflammatory markers that lasted at least six months (Shields, Spahr, & Slavich, 2020).

   GoodThese are randomized trials, though the effects are modest and come mostly from clinical samples.
5. 5

   Defuse chronic conflict before it settles in

   The chapter that praises a joyful heart also says to stop strife “before it breaks out” (Prov. 17:14). Long-term threatening stress, often relational, is what produced cortisol resistance and higher cold risk in Cohen et al. (2012). Settle disputes quickly, and do not let grudges become a standing condition.

   ModerateModerate for the stress-to-immune pathway. That conflict resolution reverses it has not been directly tested.

Studies cited on this page19

1. ↗ Bolier, L., Haverman, M., Westerhof, G. J., Riper, H., Smit, F., & Bohlmeijer, E. (2013). Positive psychology interventions: A meta-analysis of randomized controlled studies. BMC Public Health, 13, 119. https://doi.org/10.1186/1471-2458-13-119
2. ↗ Chida, Y., & Steptoe, A. (2008). Positive psychological well-being and mortality: A quantitative review of prospective observational studies. Psychosomatic Medicine, 70(7), 741–756. https://doi.org/10.1097/PSY.0b013e31818105ba
3. ↗ Coan, J. A., Beckes, L., Gonzalez, M. Z., Maresh, E. L., Brown, C. L., & Hasselmo, K. (2017). Relationship status and perceived support in the social regulation of neural responses to threat. Social Cognitive and Affective Neuroscience, 12(10), 1574–1583. https://doi.org/10.1093/scan/nsx091
4. ↗ Cohen, S., Alper, C. M., Doyle, W. J., Treanor, J. J., & Turner, R. B. (2006). Positive emotional style predicts resistance to illness after experimental exposure to rhinovirus or influenza A virus. Psychosomatic Medicine, 68(6), 809–815. https://doi.org/10.1097/01.psy.0000245867.92364.3c
5. ↗ Cohen, S., Doyle, W. J., Turner, R. B., Alper, C. M., & Skoner, D. P. (2003). Emotional style and susceptibility to the common cold. Psychosomatic Medicine, 65(4), 652–657. https://doi.org/10.1097/01.psy.0000077508.57784.da
6. ↗ Cohen, S., Janicki-Deverts, D., Doyle, W. J., Miller, G. E., Frank, E., Rabin, B. S., & Turner, R. B. (2012). Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk. Proceedings of the National Academy of Sciences, 109(16), 5995–5999. https://doi.org/10.1073/pnas.1118355109
7. ↗ Cohen, S., Janicki-Deverts, D., Turner, R. B., & Doyle, W. J. (2015). Does hugging provide stress-buffering social support? A study of susceptibility to upper respiratory infection and illness. Psychological Science, 26(2), 135–147. https://doi.org/10.1177/0956797614559284
8. ↗ Cregg, D. R., & Cheavens, J. S. (2021). Gratitude interventions: Effective self-help? A meta-analysis of the impact on symptoms of depression and anxiety. Journal of Happiness Studies, 22(1), 413–445. https://doi.org/10.1007/s10902-020-00236-6
9. ↗ Dowlati, Y., Herrmann, N., Swardfager, W., Liu, H., Sham, L., Reim, E. K., & Lanctôt, K. L. (2010). A meta-analysis of cytokines in major depression. Biological Psychiatry, 67(5), 446–457. https://doi.org/10.1016/j.biopsych.2009.09.033
10. ↗ Doyle, W. J., Gentile, D. A., & Cohen, S. (2006). Emotional style, nasal cytokines, and illness expression after experimental rhinovirus exposure. Brain, Behavior, and Immunity, 20(2), 175–181. https://doi.org/10.1016/j.bbi.2005.05.005
11. ↗ Eisenberger, N. I., Berkman, E. T., Inagaki, T. K., Rameson, L. T., Mashal, N. M., & Irwin, M. R. (2010). Inflammation-induced anhedonia: Endotoxin reduces ventral striatum responses to reward. Biological Psychiatry, 68(8), 748–754. https://doi.org/10.1016/j.biopsych.2010.06.010
12. ↗ Howren, M. B., Lamkin, D. M., & Suls, J. (2009). Associations of depression with C-reactive protein, IL-1, and IL-6: A meta-analysis. Psychosomatic Medicine, 71(2), 171–186. https://doi.org/10.1097/PSY.0b013e3181907c1b
13. ↗ Li, S., Stampfer, M. J., Williams, D. R., & VanderWeele, T. J. (2016). Association of religious service attendance with mortality among women. JAMA Internal Medicine, 176(6), 777–785. https://doi.org/10.1001/jamainternmed.2016.1615
14. ↗ Miller, A. H., & Raison, C. L. (2016). The role of inflammation in depression: From evolutionary imperative to modern treatment target. Nature Reviews Immunology, 16(1), 22–34. https://doi.org/10.1038/nri.2015.5
15. ↗ Pressman, S. D., & Cohen, S. (2005). Does positive affect influence health? Psychological Bulletin, 131(6), 925–971. https://doi.org/10.1037/0033-2909.131.6.925
16. ↗ Shields, G. S., Spahr, C. M., & Slavich, G. M. (2020). Psychosocial interventions and immune system function: A systematic review and meta-analysis of randomized clinical trials. JAMA Psychiatry, 77(10), 1031–1043. https://doi.org/10.1001/jamapsychiatry.2020.0431
17. ↗ Slavich, G. M., & Irwin, M. R. (2014). From stress to inflammation and major depressive disorder: A social signal transduction theory of depression. Psychological Bulletin, 140(3), 774–815. https://doi.org/10.1037/a0035302
18. ↗ Stellar, J. E., John-Henderson, N., Anderson, C. L., Gordon, A. M., McNeil, G. D., & Keltner, D. (2015). Positive affect and markers of inflammation: Discrete positive emotions predict lower levels of inflammatory cytokines. Emotion, 15(2), 129–133. https://doi.org/10.1037/emo0000033
19. ↗ Steptoe, A., Wardle, J., & Marmot, M. (2005). Positive affect and health-related neuroendocrine, cardiovascular, and inflammatory processes. Proceedings of the National Academy of Sciences, 102(18), 6508–6512. https://doi.org/10.1073/pnas.0409174102