Final answer:
In the early 1900s, Emil Kraepelin used the term 'Manic-depressive psychosis' to describe a mental illness. Today, this condition is known as 'Bipolar disorder' which involves alternating periods of mania and depression.
Step-by-step explanation:
In the early days (1900s), Emil Kraepelin used the term 'Manic-depressive psychosis' to describe a mental illness. However, this term is no longer used today. The current term used to describe the condition that was once referred to as manic-depressive psychosis is 'Bipolar disorder.' Bipolar disorder is characterized by alternating periods of mania and depression.