to the editor: We read with interest the review of interventions for behavioral disorders in dementia. It reviewed the evidence for behavioral interventions and recommended judicious use of antipsychotics in cases when the benefit would be great and safer tactics have already failed. However, dementia is a collective term for a set of behaviors that can arise from many different biological causes. Medications appropriate for treating Alzheimer disease, the most common and best-studied dementia, may be harmful in dementias with other etiologies. Antipsychotic use may be warranted after failure of behavioral interventions in many types of dementia, but it can cause significant problems in others.

Dementia with Lewy bodies is the second most common etiology of dementia,¹ and it is becoming more common. Its three core symptoms are fluctuating level of consciousness, parkinsonian movement symptoms, and fully formed visual hallucinations. Dementia with Lewy bodies shares dopamine dysfunction with Parkinson disease. Symptoms of these two diseases commonly co-occur, with the primary diagnosis depending on which set of symptoms presented first.

Although the presence of hallucinations in patients with dementia with Lewy bodies might increase administration of neuroleptics, the dopamine dysfunction involved means that typical antipsychotic use may worsen or precipitate symptoms of Parkinson disease.² There is rarely a need to treat hallucinations if they do not cause agitation in the patient, which is often the case in dementia with Lewy bodies. The atypical antipsychotics clozapine (Clozaril) and quetiapine (Seroquel) may be better tolerated, but they have less evidence of effect. The nondopaminergic antipsychotic pimavanserin (Nuplazid) may reduce psychosis symptoms without worsening motor function.³

Interestingly, acetylcholinesterase inhibitors that only marginally help Alzheimer disease may be more effective in treating dementia with Lewy bodies. Although patients with dementia with Lewy bodies may experience higher rates of adverse effects such as falls, those who tolerate acetylcholinesterase inhibitors show improved cognition, improved activities of daily living, and reduced behavioral disturbance, some of the very goals of antipsychotic use.⁴ Unlike in patients with Alzheimer disease, these effects may be more durable, lasting at least one year.⁵

Diagnosis of the broad term dementia is not sufficient to guide appropriate treatments. Accurate detection of the underlying pathology of the behavioral disorder is crucial for understanding the best treatments, as well as improving knowledge of prognosis and family risk.