(PSYCHIATRIC TIMES) - A recent analysis that found a 40-fold increase in the diagnosis of bipolar disorder in youth has highlighted diagnostic dilemmas and prompted calls for more research studies.1
Mark Olfson, MD, MPH, professor of clinical psychiatry at the New York State Psychiatric Institute and Columbia University, along with NIMH researcher Gonzalo Laje, MD, and their colleagues analyzed data from the National Ambulatory Medical Care Survey, an annual survey of office-based physicians in which physicians or their staff record details about representative patient visits during a 1-week period.
The researchers found that in 1994 and 1995, the annual number of office visits resulting in a diagnosis of bipolar disorder among people aged 19 years or younger was approximately 25 per 100,000 youth. By 2002-2003, the number had jumped to 1003 visits per 100,000 youth. At the same time, the annual number of adult visits that resulted in a diagnosis of bipolar disorder increased almost 2-fold, from 905 to 1679 visits per 100,000 adults.
Another recent report, by Blader and Carlson,2 analyzed data from the National Hospital Discharge survey and found a 5.6-fold increase between 1996 and 2004 in the number of children and adolescents aged 5 to 13 years, and a 4-fold increase in patients aged 14 to 19 years who were discharged with a diagnosis of bipolar disorder. Bipolar disorder-related discharges among children, for example, rose from 1.3 per 10,000 US children in 1996 to 7.3 per 10,000 US children by 2004.
The precise community prevalence of bipolar disorder in young people is not known, Olfson told Psychiatric Times.
"According to the National Comorbidity Survey Replication (2001-2003), however, the overall 12-month prevalence is 0.6% for bipolar I disorder and 0.8% for bipolar II disorder. The median age at onset is 18.2 years for bipolar I and 20.3 years for bipolar II, with approximately 25% of cases of each disorder beginning by age 12 years.3 The median time from onset to first treatment for individuals with bipolar disorder is 6 years," he said.4 "On the basis of these numbers, one would expect substantially less than the 1% rate of annual youth bipolar visits in office-based medical practices as reported in our recent study."
The office visit study had some limitations, according to its authors. Diagnoses were based on the judgment of the treating physician rather than on an independent objective assessment, so it was not possible to determine what proportion of young people actually had the disorder. Neither did the study explain why the diagnosis had been applied to so many more children and adolescents than in years past.
Overdiagnosis—or correction of underdiagnosis?
"My sense, though," Olfson said, "is that some of the increase may be accounted for by the introduction of the bipolar II disorder diagnosis in the DSM-IV (1994) and a broadening of the conceptualization of bipolar spectrum disorders. However, the magnitude and rapidity of the increase in treatment of youth bipolar disorder, the predominance of boys [66.5%] in this study treated for bipolar disorder, their young age [mean, 12.8 years], and the substantial co-treatment for attention-deficit/hyperactivity disorder [ADHD, 32.2%]—all suggest the possibility of overdiagnosis. At the same time, a substantial increase in academic attention to bipolar disorder in young people may have also helped psychiatrists and other mental health professionals to correct historical under-recognition."
In their inpatient analysis, Blader and Carlson2 said that the higher rates of inpatient admissions among youth that are associated with bipolar disorder may reflect a shift in community diagnostic practices to include a broader spectrum of clinical symptoms, with bipolar disorder being diagnosed in children who display "impulsive, volatile, aggressive dyscontrol"—children in whom other diagnoses, such as ADHD, may have been used in the past. Another reason, they said, may be "upcoding" to putatively more severe conditions for reimbursement or for administrative reasons.
A broader definition of bipolar
Whatever the reasons, Jon McClellan, MD, associate professor of psychiatry at the University of Washington and coauthor of "Practice Parameter for the Assessment and Treatment of Children and Adolescents with Bipolar Disorder"5 confirmed that the "[bipolar] diagnosis is being used much more often than it had been previously."
"Whether it is an overdiagnosis or an accurate diagnosis depends on how you want to define the disorder, and that is really what has changed. The definition has become much broader than it was 10 years ago," he said.
Another confounding factor, according to McClellan, is that some mental health professionals say they are using DSM-IV-TR criteria for bipolar disorder, but when one reads their studies, they have each applied the criteria in their own way.
In addition, differences in symptom presentation between some kids and adults often makes diagnosis more challenging, McClellan told Psychiatric Times.
"There is some agreement that the patterns of illness and symptoms described in children, particularly among those under 12 years of age, do not look like the same classic disorder that has been historically defined in adults," McClellan said. "But whether or not it is the same disorder remains to be seen."
"For some youth," Olfson said, "the course of manic symptoms tends to be more persistent than episodic, as it typically is in adult bipolar disorder. In addition, some youth appear to present with irritability, impulsive aggression, and oppositionality, with fewer or no euphoric symptoms. Some symptoms of mania, such as grandiosity and an increase in goal-directed activity, are less commonly reported in younger children in whom bipolar disorder is diagnosed. Hopefully, longitudinal research that follows identified youth into adulthood will help to clarify how manic symptom patterns migrate and change over time."
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