Several Theories Try to Explain Rise in Bipolar Diagnoses

A study finding a rapid and dramatic increase in the number of youth diagnosed with bipolar disorder is raising questions about the accuracy of clinical diagnoses of child and adolescent bipolar disorder in outpatient settings.

The authors estimated that more than a 40-fold increase occurred in the number of outpatient office visits for young people up to age 19 with a diagnosis of bipolar disorder between 1994-95 and 2002-03, according to a report in the September Archives of General Psychiatry.

The number of visits for bipolar disorder during the same period also increased substantially for adults, but not as dramatically as for youth.

Using data from the National Ambulatory Medical Care Survey (NAMCS), which is conducted annually by the National Center for Health Statistics, the study found that the estimated annual number of youth office-based visits with a diagnosis of bipolar disorder increased from 25 per 100,000 population in 1994-95 to 1,003 per 100,000 in 2002-03.

Senior author and psychiatrist Mark Olfson, M.D., M.P.H., told Psychiatric News that translates into approximately 36,000 outpatient visits for the treatment of youth for bipolar illness in 1994-95 and approximately 1.6 million such visits in 2002-03.

The NAMCS samples a nationally representative group of visits to nonfederally employed office-based physicians who are primarily engaged in direct patient care. (The number of visits represented by each visit sampled by NAMCS is determined according to the sampling probability; for example, if the visit has a 1 in 1,000 probability of being sampled by NAMCS, then it represents an estimated 1,000 visits nationally.)

Using a NAMCS sample of 154 visits for youth with bipolar disorder and 808 visits for adults with bipolar disorder between 1999 and 2003, the study also compared demographic, clinical, and treatment characteristics and found that two-thirds of youth visits were by males and that just under a third of the youth had received a comorbid diagnosis of attention-deficit/hyperactivity disorder (ADHD).

What's Behind the Increase?

Olfson and other leaders in child and adolescent psychiatry agreed that there are likely many reasons for the increase, including inaccurate diagnosis.

“Unfortunately, the study does not tell us why so many more children and adolescents are being diagnosed and treated than in years past,” Olfson said. “My sense is that some of the increase may be accounted for by the introduction of the bipolar II disorder diagnosis in the DSM-IV in 1994 and the broadening conceptualization of bipolar spectrum disorders.

“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 underrecognition,” he added.“ At the same time, the magnitude and rapidity of the increase in treatment of youth bipolar disorder, the predominance of boys in this study treated for bipolar disorder, their young age, and the substantial co-treatment for ADHD all raise the possibility of overdiagnosis.”

Ellen Leibenluft, M.D., chief of the unit on bipolar spectrum disorders at the Mood and Anxiety Disorders Program at the National Institute of Mental Health, agreed.

“It's somewhat speculative, but the report does point out the ongoing issue about how to diagnose youth who have very severe irritability and ADHD, and whether they should be thought of as bipolar or not,” she told Psychiatric News. “I think the study highlights that these very severely irritable children with ADHD don't fit very well [into DSM categories]. We can give them a diagnosis of ADHD, but then that doesn't do justice to the mood disorder.”

Olfson said psychiatrists who see youth should consider incorporating screening tools or short bipolar assessment scales into their evaluations. These tools include the Child Mania Rating Scale, the parent version of the Mood Disorder Questionnaire, or the Conner's Abbreviated Parent Questionnaire.

Leibenluft said she believes clinicians should reserve a diagnosis of bipolar disorder for children or adults who have clear episodes of mania and depression. “I think if you have a child with very severe irritability and ADHD, an appropriate diagnosis might be ADHD and mood disorder NOS [not otherwise specified].”

She cautioned that practitioners who use the NOS designation “should document very clearly why it is NOS and why the child is not fitting the criteria.”

She added that these children may also have an anxiety disorder that can be related to irritability. “Clinicians really need to be doing a very comprehensive assessment for depression, anxiety, and learning disabilities that may be contributing to irritability in school,” she said.“ They should not try to fit a square peg into a round hole by diagnosing them as bipolar.”

ADHD, Bipolar Symptoms Overlap

In the comparison of demographic, clinical, and treatment characteristics between youth and adults from 1999 to 2003, Olfson and colleagues found that while 66.7 percent of the youth visits were by males, 67.6 percent of adult bipolar visits were by females.

(That finding for adult females is considerably higher than community epidemiological samples, which have shown a slight preponderance of females among patients with bipolar disorder; the reason for the much higher preponderance in the Archives study is not known for sure, but Olfson and others said it may due to the fact that the study measured office visits and may therefore reflect greater health-care-seeking behavior by women during the depressive phase, a trait that has been previously reported.)

They also found that youth were much more likely to receive a comorbid diagnosis of ADHD than adults (32.3 percent versus 3 percent).

Olfson told Psychiatric News that the symptom overlap between ADHD and bipolar disorder increases the clinical challenge of distinguishing the two conditions.

“Some symptoms, such as distractibility, pressured speech, and irritability, can be seen in ADHD as well as mania,” he said.“ Because of the risks of inadvertently treating bipolar disorder with stimulant medications, it is especially important to conduct a thorough assessment.”

Leibenluft said the gender ratio found in the study supports the hypothesis that very irritable children with ADHD are being diagnosed with bipolar disorder. “That would support the hypothesis that this is part of what has led to the increase,” she said.

She added that the National Institute of Mental Health has conducted studies of children who have classic bipolar disorder and of children who also have overlapping symptoms of ADHD. “In the classic bipolar presentation, there is a 1-to-1 gender ratio, but it's about 3 to 1 in the children with severe irritability, with a preponderance of boys.”

The study also found that most youth (90.6 percent) and adults (86.4 percent) with a bipolar diagnosis were prescribed a psychotropic medication, with comparable rates of mood stabilizers, antipsychotics, and antidepressants prescribed for both groups.

The study findings, which received wide coverage in the lay press, come as APA is beginning work on developing the fifth edition of DSM.

“This study does not provide the level of clinical detail necessary to inform DSM-V development beyond underscoring the importance of developing age-specific criteria for bipolar disorder,” Olfson told Psychiatric News. “Some of the symptoms of mania in DSM-IV, such as grandiosity and an increase in goal-directed activity, appear to be more relevant for adults than youth. Describing criteria symptoms of manic episodes in youth will be an important challenge for the developers of DSM-V.”

Leibenluft said she expects that the issue of how clinicians should be thinking about children with severe irritability and ADHD will be discussed as part of efforts to revise DSM for its next edition.

An abstract of “National Trends in the Outpatient Diagnosis of Bipolar Disorder in Youth” is posted at<http://archpsyc.ama-assn.org/cgi/content/abstract/64/9/1032>.▪