The purpose of this study is to identify factors associated with diagnostic stability of Bipolar Mood Disorder (BMD) with statistical and clinical interest.

Retrospective cohort study, in which the medical records of 916 individuals admitted to Coimbra University Hospital, between 1989 and 2008 with first diagnostic of BMD, were analysed for the following characteristics: age, gender, occupation, educational level, age at first diagnostic, number and types of hospital admissions, presence of suicide attempts, pharmacological treatments, time between first diagnostic and the new one (Schizophrenia, Delusional Disorder or Dementia), type of cognitive impairment, assessment examinations (TC-CE and EEG) and presence of co-morbidities.

The analysed sample was divided in two groups: one that kept the first diagnostic (BMD) and another that later received a different diagnostic.

Diagnostic criteria according to International Classification of Diseases- 10th edition.

4,7% of the total sample received a different diagnostic in a posterior assessment: 41,9% Schizophrenia, 4,7% Delusional Disorder and 53,5% Dementia. The factors were analyzed with traditional statistical methods and Mann-Whitney's test. The authors found five main factors with statistical significance between the two groups, namely, age, age at first diagnostic, total number of admissions and number of admissions for maniac episodes, and educational level.

The aim of the study was achieved. In clinical practice the reported characteristics must receive a special attention in patient's assessment, in order to verify the diagnostic stability and eventual evolution to another diagnostic.