Findings from one NIMH-supported study suggest that the illness may be at least as common among youth as among adults. In this study, one percent of adolescents ages 14 to18 were found to have met criteria for bipolar disorder or cyclothymia in their lifetime. In addition, close to six percent of adolescents in the study had experienced a distinct period of abnormally and persistently elevated, expansive, or irritable mood even though they never met full criteria for bipolar disorder or cyclothymia. Compared to adolescents with a history of major depressive disorder and to a never-mentally-ill group, both the teens with bipolar disorder and those with subclinical symptoms had greater functional impairment and higher rates of co-occurring illnesses (especially anxiety and disruptive behavior disorders), suicide attempts, and mental health services utilization. The study highlights the need for improved recognition, treatment, and prevention of even the milder and subclinical cases of bipolar disorder in adolescence.

Bipolar disorder in children and adolescents has been difficult to recognize and diagnose because it does not fit precisely the symptom criteria established for adults, and because its symptoms can resemble or co-occur with those of ADHD and CD. In addition, symptoms of bipolar disorder may be initially mistaken for normal emotions and behaviors of children and adolescents. But unlike normal mood changes, bipolar disorder significantly impairs functioning in school, with peers, and at home with family.

Although research in adults indicates that the essential treatment for bipolar disorder is the use of appropriate doses of mood stabilizing medications, few studies of the safety and efficacy of these drugs have been conducted in children and adolescents. NIMH is attempting to fill the current gaps in treatment knowledge with carefully designed studies. Data from adults do not necessarily apply to younger patients, because the differences in development may have implications for treatment efficacy and safety. Thus, research in children and adolescents is needed to properly guide clinicians, patients, and families.

Current multi-site studies funded by NIMH are investigating the value of long-term treatment with lithium and other mood stabilizers in preventing recurrence of bipolar disorder in adolescents. Specifically, these studies aim to determine how well lithium and other mood stabilizers prevent recurrences of mania or depression and control subclinical symptoms in adolescents; to identify factors that predict outcome; and to assess side effects and overall adherence to treatment. Another NIMH-funded study is evaluating the safety and efficacy of valproate for treatment of acute mania in children and adolescents, and also is investigating the biological correlates of treatment response. Other NIMH-supported investigators are studying the effects of antidepressant medications in the treatment of the depressive phase of bipolar disorder in youth.

Although bipolar disorder is equally common in women and men, research indicates that approximately three times as many women as men experience rapid cycling. NIMH researchers and others are investigating possible causes for this gender difference, including greater use of antidepressant medication among women (antidepressants may induce mania or hypomania if not used in combination with a mood stabilizing drug, such as lithium or valproate), differences in thyroid activity (see below), and effects of sex hormones. Other research findings have indicated that women with bipolar disorder may have more depressive episodes and more mixed episodes than men with the illness.

A number of studies have found that among people with bipolar disorder, women are more likely than men to have a thyroid disorder. In addition, lithium treatment may cause low thyroid levels in some patients, particularly women, which may account for some depressive episodes that occur during treatment. Low thyroid levels also have been associated with rapid-cycling bipolar disorder. Thyroid hormone supplementation may be needed to restore normal thyroid levels. However, since too much or too little thyroid hormone alone can lead to mood and energy fluctuations, it is important that thyroid levels are carefully monitored in all patients with bipolar disorder.

Although bipolar disorder typically appears between early and mid-life, some people develop the disorder for the first time late in life. Research indicates that the factors contributing to late-onset bipolar disorder may differ from those influencing early-onset illness.

A recent NIMH-supported study found that older adults with late-onset bipolar disorder reported less family history of psychiatric problems, more co-occurring vascular disease, and more social support than older adults with early-onset illness. In addition, the study revealed that stressful life events were more frequent among individuals with earlier age of depressive symptom onset compared to individuals with later onset. The study findings suggest that while psychosocial factors may play an important role in early-onset illness, physical medical factors may be particularly important in late-onset bipolar disorder. Ongoing NIMH-funded research continues to investigate neuroanatomical and clinical features of bipolar disorder in older adults. This research is likely to help scientists better understand the psychobiology of bipolar disorder in older adults and may lead to better diagnosis and management of the illness in this population.