In fact, a new study reports the average delay is six years.
That lost time can result in greater frequency and severity of episodes of the psychiatric condition, the researchers said.
"While some patients, particularly those who present with psychosis, probably do receive timely treatment, the diagnosis of the early phase of bipolar disorder can be difficult," study leader Matthew Large, a professor psychiatry at the University of New South Wales, Australia, said in a school news release.
"This is because mental health clinicians are sometimes unable to distinguish the depressed phase of bipolar disorder from other types of depression," he added.
The new research reviewed the results of 27 past studies. Those studies included more than 9,400 patients.
Many patients had distressing and disruptive symptoms for many years before they received proper treatment, the researchers noted.
The delay in diagnosis and treatment was often longer for young patients because symptoms such as moodiness can sometimes be mistaken by parents and doctors as just part of being a teen, the study authors said.
"The diagnosis of bipolar disorder can also be missed because it relies on a detailed life history and corroborative information from careers and family, information that takes time and care to gather," Large explained.
He recommended that doctors look more closely at a patient's history of mood symptoms, especially distinct changes in mood and mood swings caused by outside events, such as overseas travel or treatment with antidepressants. He also suggested a closer look at mood symptoms in people who have a family history of the disorder.
A long delay in diagnosis and treatment is "a lost opportunity because the severity and frequency of episodes can be reduced with medication and other interventions," Large said.
The study was published Monday in the Canadian Journal of Psychiatry.
The American Academy of Family Physicians has more on bipolar disorder.
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