In general, mental illnesses take the patient away from the family, making his quality of life lower, and in particular, Alzheimer's disease (AD) is amental morbidity increasing faster in the world. The diagnosis of AD is predominantly clinical with the test of imaging as adjuvant; however, these tests could be difficult to obtain in developing countries. Therefore, anamnesis is the main tool in the diagnosis of AD and must be used efficiently. The propose of this critical review is to indicate a logical and scientific path for clinical procedures in the diagnosis of brain disorders, specifically for AD. Then, a literary search was made, and the subjects of the articles were directed to the descriptors clinical procedures, biochemical analysis and diagnosis. Twenty-three articles were selected, in addition was used a WHO text and two books for the ground of theory, and from that, a discussion was carried out, based on the deductive analysis of the general criteria of the psychiatric diagnosis for the specific ones, and, finally, a heuristic reasoning was associated linking the scientific method to the studied methods. Finally, the psychiatrist's preparation to carry out the anamnesis of the patient with dementia can be added to the current scientific method to make the procedure more accurate in order to avoid possible errors.