“Do Not Worry About Tomorrow”: Worry and the Body’s Stress Response

Jesus does not deny that tomorrow will have trouble. He tells us not to borrow it. The verse closes an argument that starts at 6:25: look at the birds, look at the lilies, and remember that “your heavenly Father knows that you need all these things” (6:32). The command not to worry rests on the Father’s care, and on putting “His kingdom and His righteousness” first (6:33). It is not a relaxation technique. But Jesus also makes a claim about how human beings are built: one day’s trouble is a full load. The research described below fits that claim closely.

The hypothesis. Brosschot, Gerin, and Thayer (2006) proposed the perseverative cognition hypothesis. “Perseverative cognition” is the researchers’ umbrella term for worry and rumination: the mind that keeps circling the same problem. Their point was simple. A stressful event may last a few minutes. Worry stretches the body’s response to it over hours, both before the event (anticipation) and after it (rumination). They argued that this prolonged activation, not the brief spike, does much of the long-term damage. In their review they called the evidence “preliminary support,” and that is still the honest description.

What the body does while we worry. Daily-life studies make the idea concrete. Brosschot, Van Dijk, and Thayer (2007) had 52 healthy adults keep an hourly worry diary while wearing a heart monitor. On days with more worry, heart rate was higher and heart rate variability (HRV) was lower. The effect carried into that night’s sleep, and worry duration statistically accounted for (mediated) the link between the day’s stressors and the heart’s response. Pieper and colleagues (2010) followed 73 teachers for four days. Worry episodes raised heart rate by about 2.5 beats per minute while they were happening, about 3 beats per minute in the following hour, and about 1.5 beats per minute two hours later. The stressful events themselves were not linked to heart changes in this analysis. The thinking about them was. Both studies are correlational and small, and they cannot rule out every hidden cause. Still, they do something lab studies cannot: they watch worry act on the heart in ordinary life.

A meta-analysis then pooled the evidence. Ottaviani and colleagues (2016) combined 60 studies of healthy people. In experimental studies (where researchers asked people to worry or ruminate) and in correlational studies (where people’s normal worry was measured), perseverative cognition was linked to higher heart rate, lower HRV, and higher cortisol. Cortisol is the body’s main stress hormone, and its effect was about the same size in both kinds of study (g = .36 and .32). Blood pressure rose in experimental studies, and that was the largest effect (g = .45 to .51). It was also the only result that showed signs of publication bias, meaning small studies with null results may be missing from the record. The fair summary is that worry measurably affects the heart and the hormonal stress system. The effects are small to moderate, they come from healthy people, and the blood-pressure numbers deserve the most caution.

The mechanism: a brake that worry releases. Why would a thought change the heart? Thayer and Lane’s (2000) neurovisceral integration model offers an answer. The brain’s alarm system, centered on the amygdala, is always ready to fire. The prefrontal cortex, especially its middle and lower parts just behind the forehead, acts as a brake. When the prefrontal cortex judges a situation safe, it sends inhibiting signals down through the brainstem and out along the vagus nerve, which slows the heart. That vagal brake is what HRV measures. A healthy heart does not beat like a metronome. It speeds up slightly with each breath in and slows with each breath out, and the size of that swing reflects how strongly the vagus is working. A meta-analysis of brain-imaging studies found that HRV tracks activity in exactly these regions, the amygdala and the ventromedial prefrontal cortex (Thayer et al., 2012). The authors added a striking claim: the brain’s default response to uncertainty is threat. Unless the prefrontal cortex supplies a reason to feel safe, the alarm stays on.

Worry, on this account, is a mind that keeps telling the brain it is not safe yet. Imaging studies of generalized anxiety disorder (GAD), the clinical form of chronic worry, point the same way. Etkin and colleagues (2009) found that in 16 patients the amygdala’s links to other brain networks were less distinct than in healthy controls. Makovac and colleagues (2016) scanned 19 patients and 21 controls before and after asking them to worry. In patients, amygdala-prefrontal connectivity changed as worry rose. The size of certain amygdala-connectivity changes predicted how much HRV fell. These are small imaging studies, and they show association, not proof that one thing causes the other. But they connect the anxious thought, the brain’s threat circuitry, and the heart in a single picture.

Why worry is so hard to stop. Two lines of research explain why worry feels useful while it costs us. First, intolerance of uncertainty, the felt need to know how things will turn out, is strongly linked to worry and anxiety. A meta-analysis of 181 studies and more than 52,000 people found a moderate overall correlation (r = .51) between intolerance of uncertainty and symptoms across many disorders (McEvoy et al., 2019). Second, the contrast avoidance model suggests that chronic worriers use worry to stay braced, keeping themselves in a steady negative state so that bad news never catches them off guard (Newman & Llera, 2011). Both describe the same move. We try to control tomorrow by living in it now. Jesus names the cost directly: it adds nothing to our life (Matthew 6:27) and takes away from today.

Can worry be set down? Researchers have tested a simple practice called worry postponement or stimulus control. When a worry comes up, you note it and put it off until a fixed 30-minute “worry period” each day (Borkovec et al., 1983). The results are mixed, and the paper should say so. In a randomized trial of 53 high worriers, two weeks of stimulus control reduced worry, anxiety, and insomnia more than a comparison condition did (McGowan & Behar, 2013). Among 227 Dutch schoolchildren, postponement instructions reduced how often worrisome thoughts came up (Jellesma et al., 2009). But a large online trial found no benefit (Versluis et al., 2016), and so did a study of 114 health-anxious students (Mobach et al., 2019). In a recent 14-day trial with 186 adults, postponement worked best when people made specific “if-then” plans for when and how to postpone. It cut daily worry by about 15 minutes, though sleep did not improve (McCarrick et al., 2025). The practice seems to help some people, especially when it is concrete and structured. It is not a guaranteed fix.

The convergence is this. Jesus says each day has enough trouble. The research suggests the body is built to carry today’s load: a stress response that rises and then recovers. Worry asks it to carry tomorrow’s load as well, keeping the alarm on and the vagal brake released for trouble that has not yet arrived. Jesus’ remedy, however, goes deeper than any technique. It is not “think less about tomorrow” but “your heavenly Father knows.” Trust supplies the brain’s missing safety signal from outside ourselves.

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

   Hand tomorrow to the Father on a schedule

   Set a fixed 15- to 30-minute “worry and prayer” appointment each evening, not near bedtime. During the day, when a worry about tomorrow comes up, write it in one line on a card or in your phone and say, “Not now, Lord; tonight.” When the appointment comes, go through the list: pray over each item, decide one concrete step if there is one, and release the rest (1 Peter 5:7). This is worry postponement, or stimulus control. The evidence is mixed: a small randomized trial and a large study of children found benefits, but two online and student trials did not (McGowan & Behar, 2013; Jellesma et al., 2009; Versluis et al., 2016; Mobach et al., 2019). Treat it as worth trying, not proven.

2. 2

   Make it concrete with an if-then plan

   Vague resolutions (“I’ll worry less”) rarely work. Write a specific one: “If I start rehearsing Monday’s meeting while driving, then I will say ‘Tomorrow will care for itself’ and save it for my 7 p.m. list.” In the 2025 trial, adding if-then plans to postponement cut daily worry by about 15 minutes compared with postponement alone (McCarrick et al., 2025). This is one moderately sized randomized trial, so call it promising.

3. 3

   Pray at a breathing pace

   Slow, rhythmic prayer can engage the vagal brake that worry releases. Choose a short line of Scripture, such as “The LORD is my shepherd; I shall not want,” and pray it slowly: about five seconds in, five seconds out, which is roughly six breaths a minute, for five minutes. In a small lab study (23 adults), reciting the rosary at about six breaths per minute strengthened heart-rhythm oscillations and baroreflex sensitivity, a measure of how well the body buffers swings in blood pressure (Bernardi et al., 2001). The benefit came from the breathing rhythm, not the specific words, and a yoga mantra did the same. Separately, a meta-analysis of HRV biofeedback, which trains this same slow breathing, found large drops in self-reported stress and anxiety (g = 0.83 versus controls; Goessl et al., 2017). The physiology is well supported. The idea that Scripture-paced prayer adds anything beyond the breathing has not been tested.

4. 4

   Practice trusting under uncertainty, one small step at a time

   Intolerance of uncertainty drives much of our worry (McEvoy et al., 2019). Once a week, choose one small thing you would normally over-check: re-reading an email five times, checking the forecast again, asking your wife for the third time whether the plan is set. Do it once and let it go, saying, “Your Father knows that you need all these things” (Matthew 6:32). This applies the logic of exposure work on uncertainty used in therapy for GAD. The link between intolerance of uncertainty and worry is strong (a meta-analysis of 181 studies), but this particular self-help version has not been studied as a standalone practice.

5. 5

   Don’t carry tomorrow alone

   At the end of the study, take two minutes in pairs. Each man names one worry about tomorrow, and the other prays for him, with a hand on his shoulder if both are comfortable. Section 11 reviews evidence that supportive touch and presence reduce the brain’s threat response (Coan et al.'s hand-holding research). Here the point is that saying a worry aloud to a brother moves it from silent rehearsal into shared care (Galatians 6:2). There is no direct trial of this practice for worry, so it rests on borrowed evidence and is best treated as a reasonable application.

When to get help. If worry fills most days for months, disrupts sleep, or comes with panic, it may be generalized anxiety disorder, which is common and very treatable. Seeing a counselor or physician is not a failure of faith any more than setting a broken arm is.

Studies cited on this page18

1. ↗ Bernardi, L., Sleight, P., Bandinelli, G., Cencetti, S., Fattorini, L., Wdowczyc-Szulc, J., & Lagi, A. (2001). Effect of rosary prayer and yoga mantras on autonomic cardiovascular rhythms: Comparative study. BMJ, 323(7327), 1446–1449. https://doi.org/10.1136/bmj.323.7327.1446
2. ↗ Borkovec, T. D., Wilkinson, L., Folensbee, R., & Lerman, C. (1983). Stimulus control applications to the treatment of worry. Behaviour Research and Therapy, 21(3), 247–251. https://doi.org/10.1016/0005-7967(83)90206-1
3. ↗ Brosschot, J. F., Gerin, W., & Thayer, J. F. (2006). The perseverative cognition hypothesis: A review of worry, prolonged stress-related physiological activation, and health. Journal of Psychosomatic Research, 60(2), 113–124. https://doi.org/10.1016/j.jpsychores.2005.06.074
4. ↗ Brosschot, J. F., Van Dijk, E., & Thayer, J. F. (2007). Daily worry is related to low heart rate variability during waking and the subsequent nocturnal sleep period. International Journal of Psychophysiology, 63(1), 39–47. https://doi.org/10.1016/j.ijpsycho.2006.07.016
5. ↗ Etkin, A., Prater, K. E., Schatzberg, A. F., Menon, V., & Greicius, M. D. (2009). Disrupted amygdalar subregion functional connectivity and evidence of a compensatory network in generalized anxiety disorder. Archives of General Psychiatry, 66(12), 1361–1372. https://doi.org/10.1001/archgenpsychiatry.2009.104
6. ↗ Goessl, V. C., Curtiss, J. E., & Hofmann, S. G. (2017). The effect of heart rate variability biofeedback training on stress and anxiety: A meta-analysis. Psychological Medicine, 47(15), 2578–2586. https://doi.org/10.1017/S0033291717001003
7. ↗ Jellesma, F. C., Verkuil, B., & Brosschot, J. F. (2009). Postponing worrisome thoughts in children: The effects of a postponement intervention on perseverative thoughts, emotions and somatic complaints. Social Science & Medicine, 69(2), 278–284. https://doi.org/10.1016/j.socscimed.2009.04.031
8. ↗ Makovac, E., Meeten, F., Watson, D. R., Herman, A., Garfinkel, S. N., Critchley, H. D., & Ottaviani, C. (2016). Alterations in amygdala-prefrontal functional connectivity account for excessive worry and autonomic dysregulation in generalized anxiety disorder. Biological Psychiatry, 80(10), 786–795. https://doi.org/10.1016/j.biopsych.2015.10.013
9. ↗ McCarrick, D., Prestwich, A., Ferguson, E., & O’Connor, D. B. (2025). Effects of worry postponement on daily worry and sleep: A randomised controlled trial. Psychology & Health. Advance online publication. https://doi.org/10.1080/08870446.2025.2590072
10. ↗ McEvoy, P. M., Hyett, M. P., Shihata, S., Price, J. E., & Strachan, L. (2019). The impact of methodological and measurement factors on transdiagnostic associations with intolerance of uncertainty: A meta-analysis. Clinical Psychology Review, 73, Article 101778. https://doi.org/10.1016/j.cpr.2019.101778
11. ↗ McGowan, S. K., & Behar, E. (2013). A preliminary investigation of stimulus control training for worry: Effects on anxiety and insomnia. Behavior Modification, 37(1), 90–112. https://doi.org/10.1177/0145445512455661
12. ↗ Mobach, L., van Schie, H. T., & Näring, G. W. B. (2019). Application of a worry reduction intervention in a medically unexplained symptoms-analogue student-sample. Psychology & Health, 34(6), 677–694. https://doi.org/10.1080/08870446.2018.1562066
13. ↗ Newman, M. G., & Llera, S. J. (2011). A novel theory of experiential avoidance in generalized anxiety disorder: A review and synthesis of research supporting a contrast avoidance model of worry. Clinical Psychology Review, 31(3), 371–382. https://doi.org/10.1016/j.cpr.2011.01.008
14. ↗ Ottaviani, C., Thayer, J. F., Verkuil, B., Lonigro, A., Medea, B., Couyoumdjian, A., & Brosschot, J. F. (2016). Physiological concomitants of perseverative cognition: A systematic review and meta-analysis. Psychological Bulletin, 142(3), 231–259. https://doi.org/10.1037/bul0000036
15. ↗ Pieper, S., Brosschot, J. F., van der Leeden, R., & Thayer, J. F. (2010). Prolonged cardiac effects of momentary assessed stressful events and worry episodes. Psychosomatic Medicine, 72(6), 570–577. https://doi.org/10.1097/PSY.0b013e3181dbc0e9
16. ↗ Thayer, J. F., & Lane, R. D. (2000). A model of neurovisceral integration in emotion regulation and dysregulation. Journal of Affective Disorders, 61(3), 201–216. https://doi.org/10.1016/S0165-0327(00)00338-4
17. ↗ Thayer, J. F., Åhs, F., Fredrikson, M., Sollers, J. J., III, & Wager, T. D. (2012). A meta-analysis of heart rate variability and neuroimaging studies: Implications for heart rate variability as a marker of stress and health. Neuroscience & Biobehavioral Reviews, 36(2), 747–756. https://doi.org/10.1016/j.neubiorev.2011.11.009
18. ↗ Versluis, A., Verkuil, B., & Brosschot, J. F. (2016). Reducing worry and subjective health complaints: A randomized trial of an internet-delivered worry postponement intervention. British Journal of Health Psychology, 21(2), 318–335. https://doi.org/10.1111/bjhp.12170