The elderly often with multiple diseases are particularly at risk from adverse drug reactions. Nearly half of iatrogenic drug in the elderly are preventable. Some medications such as psychotropic drugs are particularly involved in iatrogenic accidents. We wanted to know if the tools of the comprehensive geriatric assessment or other factors could influence the changes of psychotropic drugs in a geriatric departement. Our prospective study of four months in 100 patients aged 75 years and older hospitalized in the Geriatric Internal Medecine Departement of University Hospital of Nice investigated what were the clinical or biological reasons and tools used during changes of psychotropic drugs. We compared these changes according to the comprehensive geriatric assessment tools and we analyzed the changes based on lists of potentially inappropriate medications by Laroche et al. and from the instrument STOPP/START. The Mini Mental State Examination (MMSE) was the tool that has most influenced the changes in psychotropic including a tendency to increase and the introduction of anxiolytics when MMSE < 20 (p = 0.007) while neuroleptics instead arrested and decreased (p = 0.012). The comprehensive geriatric assessment has its place in decision support during the potentially iatrogenic prescriptions of drugs such as psychotropic and new tools such as STOPP/START can also be a help to the prescriber informed.