Tehran University of Medical Sciences Iranian Journal of Psychiatry 1735-4587 12 3 2017 06 28 182 187 EN Payam Amini Department of Epidemiology and Reproductive Health, Reproductive Epidemiology Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran. Roya Najafi-Vosough Department of Biostatistics, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran. Ali Ghaleiha Behavioral Disorders and Substance Abuse Research Center, Hamadan University of Medical Sciences, Hamadan, Iran Hossein Mahjub Research Center for Health Sciences and Department of Biostatistics, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran 2016 08 10 Objective: Bipolar disorder is characterized by periods of manic, depression, or mixed episodes. The purpose of this study was to assess the development of bipolar disorder episode over the time as well as determining the risk factors affecting bipolar disorder. Methods: This retrospective cohort study was conducted in Hamadan Province, the west of Iran, from April 2008 to September 2014 including 124 patients with bipolar disorder. All patients had experienced four recurrences. Generalized Estimating Equation (GEE) as a longitudinal modeling approach was used due to longitudinally recording of bipolar disorders. A significant level of 0.05 was considered for the tests. Results: The mean (SD) age of the 124 patients was 33.2 (11.55). GEE showed that the odds of manic males than depressed or mixed (as well as manic or depressed than mixed female patients according to proportionality of odds) is 1.99 times than those of females. The odds ratio of mania than depression or mixed (as well as mania or depression than mixed) is 0.441 for patients who used both drugs and psychotherapy comparing to only drugs. As well, the odds ratios comparing spring to winter and autumn are 2.01 and 1.82, respectively Conclusion: The results from this study using GEE method showed that in an Iranian bipolar disorder patients, mania is much more prevalent than depression or mixed as well as mania and depression than mixed. Sex, treatments and the seasons of recurrence can determine the episode of bipolar disorder. https://ijps.tums.ac.ir/index.php/ijps/article/view/766 https://ijps.tums.ac.ir/index.php/ijps/article/download/766/640