The impact of burn injuries on circadian rhythm and mental health

Clare Bandy

Background: Burn injuries are well-established to cause severe, systemic repercussions within the human body, leaving few systems unaffected. These consequences extend to include psychiatric health, with studies showing that burns victims are significantly more likely to be diagnosed with an axis one mental disorder. Disruption in circadian rhythm, characterised by sleep changes and hormone secretion abnormalities, among other symptoms, exist as a commonality between the two conditions, being a documented consequence of burn injuries and an enduring theory for the aetiology and maintenance of psychiatric disorders. Hypothesis: As measured by CBT, there will be a significant difference between the circadian rhythm of the Sham and Excision groups in comparison with the Burn group. After the procedure, burn injury mice will have significantly changed circadian rhythms both acutely (days) and chronically (weeks). Abnormal circadian cycles as a result of thermal injuries could lead to increased rates of mental illness. Methods: Eight-week-old female mice (n =15) were implanted with a temperature logger into the peritoneal cavity to record core body temperature (CBT) for three months. Two weeks after implantation, surviving mice received a burn injury (n = 6) to 7-8% total body surface area (TBSA), an excision injury (n = 5) to the same surface area or a sham procedure in which no injury was inflicted (n = 5). The animals were euthanised after three months and thermologgers collected. Attained data was manipulated to attain the mesor, amplitude and acrophase parameters per day. Results: There was a difference in circadian rhythm between Sham and Excision as well as Sham and Burn treatments. Burn injury was the only group to show an acute difference after procedural surgery in all parameters though Excision values also acutely changed after surgery for mesor alone. All three groups differed chronically after surgery, though only the Burn group had significantly altered acrophase in the last time-point of the experiment. Conclusion: Circadian rhythm disruptions occur after surgery. Given that surgery is so common after burn injuries, in subsequent experiments it would be logical to assess circadian rhythm changes after the procedure using gene analysis as well as by testing other parameters such as melatonin and cortisol. To link circadian rhythm disruptions to mental health problems, indicators such as mood and sleep in humans both acutely and chronically after burns and surgery should be recorded and compared with before the procedure and with healthy control populations.

The impact of burn injuries on circadian rhythm and mental health

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