Laughter is good for you: it strengthens the brain and wards off stress

Initial note: This article was originally published in the past and updated today following scientific and informative criteria. The text is for informational purposes only and does not replace medical advice.

IN BRIEF

• Laughter is associated with acute reductions in key stress markers (cortisol) in several experimental interventions and meta-analyses; however, the quality and size of studies vary considerably.
• Plausible mechanisms include the release of endogenous opioids (endorphins), modulation of the hypothalamic-pituitary-adrenal axis, and effects on the immune system (e.g., NK cell activity).
• Structured interventions such as "laughter yoga" show measurable physiological effects in controlled studies, but the evidence does not justify absolute therapeutic claims.
• The form (spontaneous vs. simulated laughter), dose, and social context influence outcomes: favorable results are more robust for short-term stress reductions than for benefits on chronic diseases.

Abstract: what does science say?

Modern research indicates that laughter can influence human physiology in measurable ways: it reduces average cortisol levels after laughter sessions, activates the endogenous opioid system, and can modulate some immune indicators. Most evidence comes from short-term experimental studies, small controlled trials, and systematic reviews; long-term benefits and effects on complex pathologies remain uncertain. The effect depends on frequency, duration, and context (social vs. isolated), as well as the nature of the laughter (spontaneous or simulated). Methodological limitations—small samples, diverse measures, risk of bias, and variability of interventions—require caution in translating results into clinical recommendations. In summary: laughter is plausibly beneficial for acute stress and subjective well-being; however, more rigorous and long-term studies are needed to establish definitive clinical impacts.

Why laugh: plausible biological mechanisms

From a biological perspective, laughter can be interpreted as a social and physiological behavior with effects on multiple systems. Neuroimaging and behavioral pharmacology studies indicate that social laughter activates reward circuits and induces the release of endogenous opioids, molecules that modulate pleasure, pain relief, and social bonding. [2]

Endorphins and the opioid system

The theory that laughter promotes endorphin release is supported by studies using proxies such as pain threshold and PET techniques for opioid receptor ligand competition: after shared laughter sessions, signals consistent with endogenous opioid release in the brain's reward areas are observed. This mechanism partly explains the increased pain threshold and immediate sense of well-being observed after laughter. [2]

Neuroendocrine response and cortisol

The hypothalamic-pituitary-adrenal (HPA) axis is key to the stress response; numerous experimental studies have measured acute variations in cortisol in saliva or blood after exposure to humorous material or guided laughter sessions. A recent meta-analysis of interventional studies showed a significant average reduction in cortisol associated with spontaneous laughter sessions compared to controls, suggesting a consistent physiological effect on acute stress. [1]

Observational and clinical evidence: what research shows

Evidence includes experimental studies, small controlled trials, and systematic reviews. Some works describe improvements in immune parameters, endocrine markers, and psychological outcomes. Results are not always consistent, but several controlled studies report favorable effects on stress indicators, immunity, and some metabolic outcomes in specific contexts. [1][3][4]

Immunity and NK cell activity

Some experimental studies have observed transient increases in Natural Killer (NK) cell activity and changes in secretory antibodies (e.g., IgA) after exposure to humorous stimuli or laughter sessions; however, methodological variability is high, and not all replications confirm clear and lasting effects. Controlled crossover studies have recorded increases in NK activity after group laughter sessions, but the evidence requires confirmation in larger samples and with longer follow-up. [4][6]

Metabolic health and other clinical outcomes

Structured interventions such as "laughter yoga" have been evaluated in more recent RCTs: some trials report attenuation of the cortisol response to controlled stress and, in studies on patients with type 2 diabetes, improvements in glycemic parameters after programs of varying duration. Such results indicate potential integrative effects on metabolic regulation related to stress reduction, although replication studies with more robust designs are still needed. [3][8]

Dosage, form, and context: how much and how to laugh?

The literature distinguishes between spontaneous laughter (genuine, triggered) and simulated laughter (e.g., laughter yoga). Narrative reviews and experimental studies show that the quality of laughter (social, shared vs. individual), the duration of exposure, and the presence of groups influence the measured effects. In general, short, repeated sessions can produce acute reductions in stress markers; shared laughter seems to provide the most powerful neurochemical stimuli, probably due to the simultaneous involvement of social signals and reward. [7][1]

Spontaneous vs. simulated

Simulated laughter can produce physiological responses similar to spontaneous ones in some measures; however, reviews emphasize that the evidence is stronger when laughter is genuine and socially contextualized. Structured interventions combining breathing, movement, and forced laughter (e.g., laughter yoga) have shown beneficial effects in RCTs, but generalizability depends on age, health status, and context. [7][3]

What it means in practice

For the general public, the results allow for some cautious and practical conclusions without turning them into clinical prescriptions: regular laughter sessions (even accompanied by group activities or breathing exercises) can help reduce short-term stress reactivity and improve subjective well-being. Short, simple, and repeated interventions (e.g., viewing humorous material, participating in social gatherings that encourage laughter, or trying laughter yoga sessions) are low-risk options that can complement stress management strategies. [1][3]

Key takeaways

• Laughter is associated with an acute reduction in cortisol in several experimental studies and meta-analyses; this supports a short-term stress-reducing effect. [1]
• Social laughter appears to activate reward systems and endogenous opioids, with possible analgesic and social bonding effects. [2]
• Some studies show transient immunological changes (e.g., NK activity), but the evidence is not yet definitive to translate these results into clinical recommendations. [4][6]
• Structured forms such as laughter yoga have shown measurable benefits in RCTs, but the variability of interventions limits the uniformity of conclusions. [3][8]
• There are no known generalized contraindications, but people with specific medical conditions should discuss new programs with their doctor.

Limitations of the evidence

Research on the role of laughter in health has some relevant methodological limitations. Many studies have small samples, crossover or quasi-experimental designs, and heterogeneous measures (plasma vs. salivary cortisol, different sampling times, various immune indicators). More recent reviews indicate average reductions in cortisol, but the effect size and its duration remain uncertain. [1]

It is important to distinguish between observed association and established causality: many studies show temporary correlations or acute effects after intervention, but long-term causal proof on clinical outcomes (e.g., reduction of cardiovascular events, remission of chronic diseases) is not available. The variability of context (social, cultural), the difficulty of blinding in trials, and possible selective publication increase the risk of overestimating effects. [1][7]

Editorial conclusion

Current evidence supports the idea that laughter is a natural behavior with measurable physiological effects, particularly on the stress response and neurochemical circuits related to social reward. Acute reductions in cortisol and activation of the endogenous opioid system offer a plausible biological framework; some immunological changes and effects on metabolic parameters are promising but require confirmation. In practical terms, promoting positive social contexts and activities that encourage laughter can be considered part of broader well-being promotion strategies, without drawing excessive or therapeutic conclusions. Larger, preregistered studies with prolonged follow-up are needed to clarify the long-term clinical impact.

Editorial note

This update has been prepared with criteria of rigor and transparency: scientific statements are supported by peer-reviewed literature with verified DOIs; prescriptive or sensationalist language has been avoided. The article is for informational purposes and does not replace personalized medical advice.

SCIENTIFIC RESEARCH

1. Kramer CK, Leitao CB. Laughter as medicine: A systematic review and meta-analysis of interventional studies evaluating the impact of spontaneous laughter on cortisol levels. PLoS One. 2023;18(5):e0286260. https://doi.org/10.1371/journal.pone.0286260
2. Manninen S, Tuominen L, Dunbar RI, et al. Social laughter triggers endogenous opioid release in humans. J Neurosci. 2017;37(25):6125–6131. https://doi.org/10.1523/JNEUROSCI.0688-16.2017
3. Meier M, Wirz L, Dickinson P, Pruessner JC. Laughter yoga reduces the cortisol response to acute stress in healthy individuals. Stress. 2021;24(1):44–52. https://doi.org/10.1080/10253890.2020.1766018
4. Takahashi K, Iwase M, Yamashita K, et al. The elevation of natural killer cell activity induced by laughter in a crossover designed study. Int J Mol Med. 2001;8(6):645–650. https://doi.org/10.3892/ijmm.8.6.645
5. Kimata H. Laughter elevates the levels of breast‑milk melatonin. J Psychosom Res. 2007;62(6):699–702. https://doi.org/10.1016/j.jpsychores.2006.12.007
6. Bennett MP, Lengacher C. Humor and Laughter May Influence Health: III. Laughter and Health Outcomes. Evid Based Complement Alternat Med. 2007;5(1):37–40. https://doi.org/10.1093/ecam/nem041
7. Mora‑Ripoll R. Potential health benefits of simulated laughter: A narrative review of the literature and recommendations for future research. Complement Ther Med. 2011;19(3):170–177. https://doi.org/10.1016/j.ctim.2011.05.003
8. Funakoshi‑Kato A, [et al.]. Laughter yoga as an enjoyable therapeutic approach for glycemic control in individuals with type 2 diabetes: A randomized controlled trial. Front Endocrinol (Lausanne). 2023;14:1148468. https://doi.org/10.3389/fendo.2023.1148468 [8]

Note: where some bibliographic details are partial or the context requires clarification, placeholders have been inserted in square brackets: [missing data if any].