Background: People with major depressive disorder (MDD) experience many different symptoms, including feeling guilty, low self-esteem with unhappiness as well as decreased capacity to enjoy life's simple pleasures. They may also experience changes in their sleep and appetite patterns, as well as feelings of hopelessness and suicidal thoughts. Depression and bipolar disorder (BD) are two of the most frequent mental diseases that lead to disability globally. Objective: To give an updated overview about bipolar depression. Methods: Bipolar depression and people with major depressive disorder were all looked for in PubMed, Google scholar, and Science direct. References from relevant literature were also evaluated by the authors, but only the most recent or complete study from January 2000 to May 2021 was included. Due to the lack of sources for translation, documents in languages other than English have been ruled out. Papers that did not fall under the purview of major scientific investigations, such as unpublished manuscripts, oral presentations, conference abstracts, and dissertations, were omitted. Conclusion: Researchers are performing numerous neuroanatomical and neuroimaging investigations to learn more about bipolar disorder. Bipolar disease is associated with impairments in neurocognitive processing abilities, which can be seen in a variety of neuropsychological domains such as psychomotor speed, attention, memory, executive function, as well as learning.