Neuropsychiatric manifestations in mild cognitive impairment: a systematic review of the literature.

BACKGROUND Mild cognitive impairment (MCI) is an etiologically heterogeneous condition that is characterized by cognitive changes without impairment of activities of daily living and insufficient to represent dementia. MCI is an important risk state for dementia. Neuropsychiatric symptoms may be present in MCI. METHODS We executed a PubMed search for articles on the neuropsychiatric manifestations in MCI and reviewed their findings. RESULTS Behavioral abnormalities are reported in 35-75% of MCI patients with the most common being depression, apathy, anxiety and irritability. The observed variability in symptom prevalence can be explained by the different sampling methods, MCI diagnostic criteria and behavioral instruments used. There is a compelling body of evidence that MCI patients with behavioral features are more prone to develop Alzheimer's disease (AD) than patients without these features. CONCLUSIONS Neuropsychiatric symptoms are common features of MCI. The behavioral changes observed in MCI are similar to those of AD and may help identify the subgroup of MCI patients with prodromal AD. Large prospective longitudinal studies would greatly contribute to our understanding of the epidemiology, diagnostic and prognostic value of the neuropsychiatric features in MCI.