Sudden stress triggers a biological reaction, the fight or flight response, which produces the release of hormones in the bloodstream. This is useful and can be lifesaving in certain cases. However, the constant presence of stress hormones in the body is harmful and long term stress takes a heavy toll on cats’ physical and mental health.
Stressors have a direct effect on the hypothalamus which releases CRH (corticotrophin−releasing hormone), a signal to the pituitary gland to secrete ACTH (adrenocorticotropic hormone). ACTH activates the adrenal glands which start releasing corticosteroids or cortisol. Cortisol is useful in restoring balance, by keeping blood sugar at a normal level, accessing fat and protein stores to compensate for spent energy. The hypothalamus also sends signals to the adrenal medulla to secrete adrenalin to arouse the sympathetic nerves, increasing heart rate, pumping more oxygen to the muscles, switching off the immune system, making the body ready to fight or flee.
As soon as the stressor has been eliminated, homeostasis is restored, but if the stress response continues, health problems appear.
Clinical signs of prolonged stress are varied and more or less severe:
Excessive grooming or pulling out of fur can be signs of anxiety and stress. Pica or fabric eating are similar symptoms, due to low levels of serotonin and high levels of adrenalin. These behaviours might be a way for the cat to achieve some sort of relaxation.
Agitation, nervousness, excessive meowing or sleep disturbances are manifestations of a constant state of alert, here again caused by cortisol and adrenalin.
Another sign is depression, due to low levels of serotonin. Indeed, in the stress response, the sympathetic system kicks in and the parasympathetic system takes a back seat, causing serotonin levels to remain low. The clinical signs can be timidity, hiding away under furniture and even in litter boxes.
Spraying or depositing faeces are usually signs of territorial stress: when a cat detects a risk of intrusion in its territory, a stress response will occur and the cat will spray and leave faeces exposed, at the same time as it will brace itself for a possible fight. Once the risk is gone, everything will go back to normal. In a multi cat household, the same sort of situation could be experienced by a cat, causing the same behaviour but this time with no resolution as the stressor remains.
More serious syndromes can be brought about by prolonged stress:
Overeating and as a consequence, weight gain, can be a clinical sign of chronic stress. Weight gain could also be a consequence of a change in metabolism: high levels of cortisol in the bloodstream can disrupt the metabolic rate. Cortisol keeps blood sugar and insulin levels high (stress-induced hyperglycemia) and this could result in the onset of type 2 diabetes. Interestingly, the opposite can happen and loss of appetite and weight loss can be a sign of chronic stress as cortisol also decreases the function of the digestive system.
The stress hormones cortisol and adrenaline impair the immune system, can make the body prone to infection and inflammation. Diseases like feline idiopathic cystitis (FIC) and bordetella, an acute respiratory infection have also been associated with stress. Episodes of FIC have been shown to be triggered by stressful events in affected cats and fits of coughing brought on by stress in cats with bordetella.
Finally, ischaemia and heart disease can also be the result of chronic stress : blood pressure being kept high because of cortisol and a constantly high heart rate can lead to atherosclerosis, damaged lining of the blood vessels’ walls, blockages, etc.
Stressors have a direct effect on the hypothalamus which releases CRH (corticotrophin−releasing hormone), a signal to the pituitary gland to secrete ACTH (adrenocorticotropic hormone). ACTH activates the adrenal glands which start releasing corticosteroids or cortisol. Cortisol is useful in restoring balance, by keeping blood sugar at a normal level, accessing fat and protein stores to compensate for spent energy. The hypothalamus also sends signals to the adrenal medulla to secrete adrenalin to arouse the sympathetic nerves, increasing heart rate, pumping more oxygen to the muscles, switching off the immune system, making the body ready to fight or flee.
As soon as the stressor has been eliminated, homeostasis is restored, but if the stress response continues, health problems appear.
Clinical signs of prolonged stress are varied and more or less severe:
Excessive grooming or pulling out of fur can be signs of anxiety and stress. Pica or fabric eating are similar symptoms, due to low levels of serotonin and high levels of adrenalin. These behaviours might be a way for the cat to achieve some sort of relaxation.
Agitation, nervousness, excessive meowing or sleep disturbances are manifestations of a constant state of alert, here again caused by cortisol and adrenalin.
Another sign is depression, due to low levels of serotonin. Indeed, in the stress response, the sympathetic system kicks in and the parasympathetic system takes a back seat, causing serotonin levels to remain low. The clinical signs can be timidity, hiding away under furniture and even in litter boxes.
Spraying or depositing faeces are usually signs of territorial stress: when a cat detects a risk of intrusion in its territory, a stress response will occur and the cat will spray and leave faeces exposed, at the same time as it will brace itself for a possible fight. Once the risk is gone, everything will go back to normal. In a multi cat household, the same sort of situation could be experienced by a cat, causing the same behaviour but this time with no resolution as the stressor remains.
More serious syndromes can be brought about by prolonged stress:
Overeating and as a consequence, weight gain, can be a clinical sign of chronic stress. Weight gain could also be a consequence of a change in metabolism: high levels of cortisol in the bloodstream can disrupt the metabolic rate. Cortisol keeps blood sugar and insulin levels high (stress-induced hyperglycemia) and this could result in the onset of type 2 diabetes. Interestingly, the opposite can happen and loss of appetite and weight loss can be a sign of chronic stress as cortisol also decreases the function of the digestive system.
The stress hormones cortisol and adrenaline impair the immune system, can make the body prone to infection and inflammation. Diseases like feline idiopathic cystitis (FIC) and bordetella, an acute respiratory infection have also been associated with stress. Episodes of FIC have been shown to be triggered by stressful events in affected cats and fits of coughing brought on by stress in cats with bordetella.
Finally, ischaemia and heart disease can also be the result of chronic stress : blood pressure being kept high because of cortisol and a constantly high heart rate can lead to atherosclerosis, damaged lining of the blood vessels’ walls, blockages, etc.