Bipolar disorder in the International Classification of Diseases-Eleventh version: A review of the changes, their basis, and usefulness

Table 5 Controversies about type two bipolar disorder

Controversy	For retaining BP-II disorder	Against retaining BP-II disorder
The definition of hypomania	Current definitions of BP-II disorder in the ICD-11 and the DSM-5 represent an optimal balance between sensitivity and specificity; they will prevent the over-diagnosis and harmful effects of inappropriate treatment of a false positive diagnosis[30,38,42,43]	Current criteria are too restrictive and under-diagnose hypomania and BP-II disorder. The minimum duration required is not evidence-based and should be shorter[32,113,114,120,121]
Prevalence of BP-II disorder	The prevalence of BP-II disorder is as high as BP-I disorder, or even higher than the BP-I subtype[98,108-110]	Data on prevalence are mixed. Prevalence is also influenced by factors such as broader definitions, improved recognition, and increased awareness[111,114]
Course of BP-II disorder	Compared to BP-I disorder, BP-II disorder has a more chronic course, greater syndromal and subsyndromal depressive symptoms, and higher episode frequency[98,107-109,112]	The seemingly adverse course of BP-II disorder could be a function of confounding factors such as symptom-severity, comorbidity, and the effects of treatment[32,70,99,114]
Diagnostic stability of BP-II disorder	The diagnosis of BP-II disorder remains the same for several years. Only 5%-15% of the patients with BP-II disorder develop BP-I disorder[6,98,105,109]	The boundaries between BP-II and BP-I disorder, between BP-II disorder and cyclothymia, and between BP-II disorder and personality disorders are unclear[70,99,113,115]
The prevalence of psychotic symptoms	Patients with BP-I disorder are more likely than those with BP-II disorder to have psychotic symptoms[66,111,115]	Psychosis is also associated with hypomania, especially in longitudinal community studies[68,69,113]
Suicidal behaviour	Suicide rates are higher in BP-II disorder than BP-I disorder[107-109,120,121]	The higher suicide rates in BP-II disorder could be a function of comorbid personality disorders and comorbid substance use[98]
Family-genetics	BP-II disorder runs in families. Genetic studies help distinguish BP-II disorder from BP-I disorder[98,110,116,118,121]	Genetic studies show that BP-II and BP-I disorders lie on a continuum of genetic risk without any distinction between the two subtypes[106,112,114,120]
Neuroimaging	Some studies suggestquantitative or qualitative differences between the two subtypes[116,123]	There are no differences in neuroimaging between the two subtypes[98,111,112,114,120]
Neurocognition	Patients with BP-II disorder are less impaired on neuropsychological tests than those with BP-I disorder[98]	There is a great degree of overlap in the neurocognitive performance between the two subtypes[114,116]
Treatment response	The treatment requirements of patients with BP-II disorder are different[115,118,119]	There is no difference in treatment response between the two subtypes[98,108,111,114,120]

BP-I: Type I bipolar disorder; BP-II: Type II bipolar disorder; DSM-5: Diagnostic and Statistical Manual of Mental Disorders, 5^th edition[6]; ICD-11: International Classification of Diseases, 11^th version[8].