Causes and diagnosis of problems
What makes a pet misbehave?
Behavior problems can be due to either medical or psychological causes, or
indeed both. A combination of a thorough clinical history, complete physical
examination, and range of appropriate diagnostic tests will determine if there
are underlying medical conditions contributing to the problem. Although there
may be a single cause for a behavior problem it is often the combined effect
of the environment and learning on the pet's mental and physical health that
determines behavior. For example, the pet that is fearful of children, may begin
to become more reactive, irritable and aggressive as diseases such as dental
problems or arthritis make it more uncomfortable, painful or less mobile. If
the display of aggression causes the children to retreat then learning will
take place and the dog will be more likely to display threatening behavior when
it next encounters a child.
What are some psychological causes of behavior problems?
Any change in the environment may contribute to the emergence of behavior problems.
For example, moving house, changing routines, adding new members to the household
(for example in the form of a baby, a spouse or a new pet) or losing existing
members through death or re homing can all have a dramatic impact on behavior.
Of course such impact may be emphasized in some individuals and there is scope
for inter play between environmental factors and medical factors. For example
degenerative changes associated with ageing may cause the pet to be more sensitive
to these environmental changes and so display more marked behavioral responses
Learning also plays a role in most behavior problems. Learning theory is a
very complex subject, but in simple terms it involves the processes of reinforcement
or punishment. When a pet's actions result in unpleasant consequences (for example
discomfort or lack of attention) the chances of repeating the behavior will
decrease. This is the process of punishment. If the behavior is followed by
pleasant consequences such as obtaining food, attention, or affection (rewards),
the performance of the behavior will increase. This is the process of reinforcement.
Both of these processes can occur unintentionally. For example when a pet raids
the dustbin and finds some appealing leftovers its behavior of raiding the bin
is rewarded and is likely to increase. Likewise if a puppy approaches a stranger
whilst out on a walk and the stranger unintentionally stands on its foot the
behavior of greeting strangers may be unintentionally punished and decrease,
unless appropriate action is taken. Unintentional reinforcement can be a particular
problem since reinforcement maintains behavior problems and in many cases it
can be difficult to determine what the rewarding stimulus is for a particular
What tests can be done to determine a psychological cause?
A good history is one of the most important means of determining the cause
of a behavioral problem. This involves an in depth analysis of the pet's medical
and behavioral past, including any training, as well as the circumstances surrounding
the problem itself. Daily interactions with the pet and any changes in routine
need to be explored. Often the event that precipitated the behavioral change
is long since past and the circumstances that are responsible for maintaining
are of more relevance.
Based on the presenting behavioral signs, the pet's age, sex and health status
and the results of a physical examination, the veterinary surgeon will determine
if there are any possible medical causes or contributing factors. Diagnosis
of a purely psychological cause can only be made after all medical factors have
been ruled out.
What medical conditions can cause or contribute to behavior problems?
Examples of medical conditions that can cause or contribute to behavior problems
include any decline in the pet's hearing, sight or other senses, any organ dysfunction
(e.g. liver or kidney disease), hormonal diseases, diseases affecting the nervous
system, diseases of the urinary tract (infections, tumors or stones), any disease
or condition that might lead to pain or discomfort, and conditions that affect
the pet's mobility.
a) Any condition that leads to an increase in pain or discomfort can lead to increased
irritability, increased anxiety or fear of being handled or approached, and ultimately
an increase in "aggressive" behavior. If these aggressive displays are
successful at removing the "threat" (and they usually are) the behavior
is reinforced. Medical conditions that affect the ears, anal sacs, teeth and gums,
bones, joints, or back (disks) are some of the more common causes of pain and
discomfort. If the pet's mobility is affected, it may become increasingly aggressive
as it chooses to threaten and bite, rather than retreat. A decrease in mobility
could also affect elimination disorders involving both urination and defecation,
as the pet's desire or ability to utilize its elimination area decreases.
b) Sensory dysfunction: Pets with diminished sight or hearing may have a decreased
ability to detect or identify stimuli, and might begin to respond differently
to commands, sounds or sights. Sensory decline is more likely to be seen in
c) Diseases of the internal organs, such as the liver or kidneys, can cause
a number of behavior changes, primarily due to the toxic metabolites that accumulate
in the bloodstream. Organ decline and dysfunction is more common in the older
pet. Any medical conditions that cause an increased frequency of urination or
decreased urine control, such as kidney disease, bladder infections, bladder
stones, or neurological damage might lead to an increase in house soiling. Similarly,
those problems that affect the frequency of bowel movements or bowel control,
such as colitis or constipation might lead to house soiling with feces.
d) Diseases of the brain and spinal cord can lead to a number of behavior and
personality changes. Conditions such as epilepsy, brain tumors, infections and
immune and degenerative diseases can all directly affect a dog or cat's nervous
system and therefore its behavior. In the older pet ageing changes can have
a direct effect on the brain, leading to behavioral signs associated with senility.
e) The endocrine (hormone) system also plays a critical role in behavior. Over-activity
or under-activity of any of the endocrine organs can lead to a number of behavior
problems. The thyroid and parathyroid glands (in the neck), the pituitary gland
(in the brain), the adrenal gland (by the kidneys), the pancreas, and the reproductive
organs can all be affected by conditions or tumors that lead to an increase
or decrease in hormone production. Endocrine disorders are more likely to arise
as the pet gets older.
f) The ageing process is associated with progressive and irreversible changes
of the body systems. Although these changes are often considered individually,
the elderly pet is seldom afflicted with a single disease, but rather with varying
degrees of organ disease and dysfunction. Cognitive decline and senility have
also been recognized in older dogs (and perhaps cats).
What tests need to be done to determine if my pet's behavior problem is
due to a medical condition?
Clinical history and physical examination
The assessment begins with a clinical history and thorough physical examination.
Laboratory tests may also be needed. More in depth investigation for example via
neurological examinations or sensory testing may be required. For some of these
tests your pet may need to be referred to a specialist.
Medical, surgical, dietary or pharmacological treatment
Before beginning behavior therapy, any medical problem that has been diagnosed
should be treated. A change in diet or a trial period of drug therapy may be
an important aspect of differentiating a medical from a behavioral cause (for
example a food trial might be used to rule out dietary allergies or antibiotic
therapy may be necessary to rule out dermatological involvement). Surgery may
also be indicated, for example when a tumor is diagnosed or when neutering is
indicated to reduce hormonally dependent behaviours. For long-standing and/or
severe behavior problems your veterinary surgeon may use a combination of medical
and behavioral treatment.
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