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Depression is an increasingly prevalent and frequently difficult-to-treat chronic disorder. As rates have increased worldwide,¹ especially among youth and young adults,² it is well known that antidepressant medications do not provide adequate symptom relief for most and are wholly ineffective for many patients.³ This is likely due at least in part to the fact that depression, like most chronic conditions, has a multitude of causes, meaning that one person’s “depression” is not necessarily like another’s. Depression caused by different mechanisms is likely to respond very differently to a given treatment. This suggests that the ability to identify a common mechanism related to depressive symptoms could lead to novel therapies for at least a subset of these patients. Now, a new study reports evidence suggesting that body temperature is related to depression, implying that a potential treatment approach for at least some people may be cooling the body.⁴ The results also suggest that body temperature elevation might be used as an indicator for a subtype of depression that involves underlying mechanisms that result in such elevation.

While several smaller studies using controlled conditions have hinted at a potential connection between body temperature and depression,^5,6 this new study examined the relationship in over 20,000 people over the course of seven months as part of the TemPredict Study and found that higher body temperature was significantly associated with self-reported depression symptoms. Participants wore an Oura Ring that collected distal body temperature, completed daily surveys that asked for a self-collected body temperature measurement assessed with a handheld thermometer, and took monthly PROMIS mental health assessments.⁴

The researchers found that higher self-reported and wearable sensor-assessed body temperatures when awake was associated with greater depression symptom severity and that this effect was dose dependent: each increasing level of depression symptom severity was associated with even higher body temperatures. They also found a trend toward lower diurnal body temperature amplitude (the difference between highest and lowest daily temperature) being associated with greater depression symptom severity, but it was not statistically significant.⁴

Several smaller studies have also found that when people experiencing depression recover, their elevated body temperature also goes away,^7,8 suggesting that the two are directly related and that perhaps interventions that lower body temperature may help alleviate symptoms at least temporarily. It is tempting to think that hormetic cold exposure could work to alleviate depression symptoms, and that has been found in some small studies, but the effect was found immediately after the cold exposure.^9,10 However, it may actually be more effective to do just the opposite: expose the body to higher heat, such as hot yoga or sauna, inducing the body’s compensatory cooling mechanism. Indeed, small studies have found more lasting impacts of heat therapies on alleviating depression symptoms.^11-13 In at least one of these studies, people with higher body temperatures prior to the hyperthermic treatment tended to experience larger antidepressant responses.¹³

So what might be the mechanism behind this relationship? One thing that comes to mind is inflammation, which is associated with some subtypes of depression¹⁴ and also, of course, with increased temperature. It’s unclear if this association with body temperature appears in all types of depression or just some, and the effect is large enough to be significant, despite not being found in all patients. Additionally, the study authors note that body temperature reflects a balance between metabolic heat generation and thermoregulatory heat loss, and problems with either of these processes (or both) could result in higher temperatures. This brings to mind the potential that the HPTA axis could be involved, or autonomic nervous system dysregulation.

Finally, it is important to note here that association does not necessarily imply causation. While it is likely that temperature elevations are an effect and not a cause, both it and depression itself may be effects of some upstream cause or causes. That said, if treatments like cold or heat exposure can treat both the elevated temperature and alleviate symptoms, they could be an important, easy, low-cost lifestyle treatment to consider as an adjunctive therapy, at least for some patients. It may also be that only people with certain subtypes of depression have this elevation, and its presence might then be used as a diagnostic indicator that helps inform how to proceed with other assessments and interventions to address the underlying causes.

References

1. World Health Organization. Depressive disorder (depression). WHO. Published March 31, 2023. Accessed February 14, 2024. https://www.who.int/news-room/fact-sheets/detail/depression
2. National Institute of Mental Health. Major depression. NIMH. Updated July 2023. Accessed February 14, 2024. https://www.nimh.nih.gov/health/statistics/major-depression
3. Cipriani A, Furukawa TA, Salanti G, et al. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis. Focus (Am Psychiatr Publ). 2018;16(4):420-429. doi:1176/appi.focus.16407
4. Mason AE, Kasl P, Soltani S, et al. Elevated body temperature is associated with depressive symptoms: results from the TemPredict Study. Sci Rep. 2024;14(1):1884. doi:1038/s41598-024-51567-w
5. Tocchetto BF, Ramalho L, Zortea M, et al. Peripheral body temperature rhythm as a marker of the severity of depression symptoms in fibromyalgia. Biol Psychol. 2023;177:108494. doi:1016/j.biopsycho.2023.108494
6. Rausch JL, Johnson ME, Corley KM, et al. Depressed patients have higher body temperature: 5-HT transporter long promoter region effects. Neuropsychobiology. 2003;47(3):120-127. doi:1159/000070579
7. Szuba MP, Guze BH, Baxter LR Jr. Electroconvulsive therapy increases circadian amplitude and lowers core body temperature in depressed subjects. Biol Psychiatry. 1997;42(12):1130-1137. doi:1016/S0006-3223(97)00046-2
8. Avery D, Wildschiødtz G, Rafaelsen OJ. REM latency and temperature in affective disorder before and after treatment. Biol Psychiatry. 1982;17(4):463-470.
9. Rymaszewska J, Lion KM, Pawlik-Sobecka L, et al. Efficacy of the whole-body cryotherapy as add-on therapy to pharmacological treatment of depression—a randomized controlled trial. Front Psychiatry. 2020;11:522. doi:3389/fpsyt.2020.00522
10.  Kelly JS, Bird E. Improved mood following a single immersion in cold water. Lifestyle Med. 2022;3(1):e53. doi:1002/lim2.53
11.  Janssen CW, Lowry CA, Mehl MR, et al. Whole-body hyperthermia for the treatment of major depressive disorder: a randomized clinical trial [published correction appears in JAMA Psychiatry. 2016;73(8):878]. JAMA Psychiatry. 2016;73(8):789-795. doi:1001/jamapsychiatry.2016.1031
12.  Nyer M, Hopkins LB, Farabaugh A, et al. Community-delivered heated hatha yoga as a treatment for depressive symptoms: an uncontrolled pilot study. J Altern Complement Med. 2019;25(8):814-823. doi:1089/acm.2018.0365
13.  Hanusch KU, Janssen CH, Billheimer D, et al. Whole-body hyperthermia for the treatment of major depression: associations with thermoregulatory cooling. Am J Psychiatry 2013;170(7):802-804. doi:1176/appi.ajp.2013.12111395
14.  Beurel E, Toups M, Nemeroff CB. The bidirectional relationship of depression and inflammation: double trouble. Neuron. 2020;107(2):234-256. doi:1016/j.neuron.2020.06.002