[9] Other definitions of unipolar mania in research include, at least three manic episodes without the experience of a depressive period for the length of the study.
In Nurnberger's study, a 4-month follow up was conducted, and in this time 29% of unipolar mania cases were reclassified as true bipolar disorder.
The study involved selecting 40 patients from both countries and researchers found that unipolar mania was three times more common in Tunisia than in France.
Longitudinal studies have been used to assess the validity of unipolar mania as a separate diagnosis and to distinguish it from bipolar I disorder.
Solomon et al. (2003) looked at the condition of participants when they first entered the study and followed up on them for a period of 15 years.
This was done through the use of the Longitudinal Internal Follow-Up Evaluation, looking at the participants psychopathology, every 6 months for the first 5 years and then on an annual basis.
Hence, illustrating, the prevalence of unipolar mania as a distinct condition, however due to being a rare entity, claiming for it to be a separate diagnosis needs further research and evidence.
Although this form of research has various limitations, it has managed to yield valuable data in exploring the phenomenon of unipolar mania further.
The study consisted of a group of 38 patients, aged 18–65, who met the diagnostic category for unipolar mania as they had experienced a minimum of four manic episodes and were in the euthymic period.
The second group consisted of 42 patients, aged 18–65, who were diagnosed with bipolar I disorder (as per the DSM-IV), due to previously experiencing both manic and depressive episodes whilst also being in the euthymic period.
There also remains uncertainty whether unipolar mania is separate to bipolar disorder and researchers including Yazıcı have raised concerns about its diagnosis.
[12] There is also research showing that clinical features and socio-demographic characteristics of bipolar disorder and unipolar mania patients are homogenous; any differences are non-significant.
[16][18] With disparities in both diagnosis criteria and research findings, as well as the small sample sizes in the studies, unipolar mania as a separate disorder is under scrutiny.