A change in behavior is often the earliest and most subtle sign of illness. Because animals cannot verbalize symptoms, the astute veterinarian relies heavily on reports from owners and direct observation.
Therefore, the standard of care for any presenting behavioral complaint must include a thorough physical examination and diagnostic workup before diagnosing a purely behavioral disorder. Conversely, any animal presenting with a chronic, treatment-resistant medical condition should be evaluated for underlying stress or anxiety. A change in behavior is often the earliest