Problem behaviour in veterinary patients is often interpreted through a behavioural label before competing clinical explanations have been adequately separated. This is problematic because similar observable phenotypes can arise from pain, fear or anxiety, learned contingencies, environmental mismatch, social or handling conflict, neurological dysfunction, endocrine or other medical disease, or several causes acting concurrently. This article develops an original non-empirical clinical-behaviour framework for differentiating these possibilities without assuming that behavioural topography identifies aetiology. The synthesis treats history, direct observation, clinical examination, context change, diagnostic testing, and response to intervention as distinct evidence streams whose meaning depends on species, age, temporal pattern, setting, and measurement quality. Pain-associated behavioural change is separated from primary fear; learned maintenance is distinguished from initiating causes; environmental and handling effects are treated as context-dependent contributors rather than default diagnoses; and neurological or medical explanations remain active when temporal or clinical evidence warrants them. The principal contribution is a proposed behaviour–medicine differentiation architecture in which diagnostic confidence increases through convergence across independent evidence streams and is reduced by discordance, masking, observer effects, or context specificity. Therapeutic response is treated as evidence of modifiability rather than proof of original cause. The framework is intended to improve clinical reasoning and welfare-sensitive reassessment, not to provide a validated diagnostic score. Its principal limitations are evidence heterogeneity, concentration on companion dogs and cats, and absence of prospective external validation of the integrated architecture.
