[Unexplained behaviour and dementia].

Behavioural changes, often resulting in negative or challenging behaviour, are highly prevalent in patients with dementia. Here we describe two patients in whom challenging behaviour was the first sign of an evolving dementia process. We discuss the relevance of a multifactorial approach in analysis and treatment, starting from a biopsychosocial model of behaviour in dementia. One pitfall is underestimating the contribution of physical co-morbidity to challenging behaviour in these patients; a further pitfall is the 'attribution phenomenon', i.e. the tendency to attribute new behavioural symptoms to conditions that are already known, such as chronic psychiatric illness. Guidelines for the assessment and management of challenging behaviour in patients who have already been diagnosed with dementia are also useful in cases where the physician is confronted with unexplained behavioural changes and challenging behaviour in older adults who have not yet been diagnosed with this condition.