context: The bipolar spectrum is a term used to refer to conditions that include not only bipolar disorder as traditionally defined (that is, clear episodes of mania or hypomania as well as depressive syndromes) but also other types of mental conditions that can involve depression or mood swings without manic or hypomanic episodes -- including some impulse control disorders, anxiety disorders, personality disorders, and forms of substance abuse. Some psychiatrists find the "bipolar spectrum" concept to be a useful framework for thinking about the driving force behind a wider range of mental health problems. Others, however, argue that symptoms alone often aren't diagnostic, and may reflect other conditions that have their own unique causes and treatments; critics also point out that treatments used for bipolar I or II disorder may not necessarily be safe or effective for conditions that only "loosely" resemble bipolar disorder. Bipolar disorder is traditionally defined by four main forms: In bipolar I disorder, a person has at least one manic episode lasting at least a week. He or she also has multiple episodes of major depression. Without treatment, the episodes of depression and mania usually repeat over time. Time spent with depressive symptoms, may outnumber time spent with mania symptoms by about 3 to 1. In bipolar II disorder, a person has a milder form of mania, called hypomania, lasting several days or longer. Periods of depression, though, outnumber the time spent with symptoms of hypomania by almost 40 to 1 in many people with this form of the disorder. Because hypomania can be mistaken for ordinary happiness or even normal functioning, bipolar II may often be misdiagnosed as depression alone (unipolar depression). In bipolar disorder not otherwise specified (more recently called "not elsewhere classified"), people have symptoms of mania or hypomania that are too few in number or too short in duration to meet currently accepted definitions of a manic or hypomanic syndrome or episode. In cyclothymic disorder (sometimes unofficially called bipolar III), a person has hypomanias (as in bipolar II disorder) that alternate frequently with brief periods of depression. When present, though, the symptoms of depression do not last long enough and involve enough symptoms to define major depression as a full syndrome. The concept of a bipolar spectrum may include additional subtypes of bipolar disorder that were proposed in the 1980s. Those subtypes include: Bipolar IV, identified by manic or hypomanic episodes that occur only after taking antidepressant medications Bipolar V, which refers to patients who have a family history of bipolar disorder but only have symptoms of major depression themselves The symptoms described by these last two subtypes have long been known to exist. But they have not been rigorously studied enough to warrant their being made distinct diagnostic categories. The idea of a broader "bipolar spectrum" involves the idea that people with certain other mental conditions may be in the bipolar spectrum. Mental or behavioral conditions that share some common features with bipolar disorder, and are therefore sometimes included within a possible bipolar spectrum, include: Highly recurrent or treatment-resistant depression Impulsive disorders Substance abuse disorders Eating disorders, such as anorexia and bulimia Personality disorders, such as borderline personality disorder Childhood behavioral disorders, such as conduct disorder or disruptive mood dysregulation disorder Researchers are still trying to determine when and how conditions such as these may overlap with bipolar disorder in terms of symptoms, underlying biology, and possible treatment implications. A number of mental conditions other than bipolar disorder share symptoms that overlap across disorders. For example, many people with borderline personality disorder experience depression or substance use disorders experience depression along with severe mood swings and problems with impulse control. People with ADHD and bipolar disorder may similarly experience distractibility and problems with attention. Although these disorders do not meet the diagnostic criteria for bipolar illness, some psychiatrists believe they have something important in common with people with bipolar disorder. Symptoms that may overlap between bipolar spectrum conditions and bipolar disorder include: Depression with very sudden or frequent mood swings (seen in many mental conditions) Prolonged irritability (which may be more common in mania than depression) Impulsivity (common during manic episodes) Euphoria and high energy (which can sometimes occur in substance abusers even when they are not intoxicated or "high" from the effects of drugs) Because the cause of bipolar disorder isn't known, it's difficult for experts to know the real overlap between bipolar disorder and a possible broader bipolar spectrum. Another implication of non-bipolar-disorder conditions falling within a broader bipolar spectrum is the possibility that medicines used to treat bipolar disorder might have value in other disorders. Psychiatrists have long known that mood stabilizers, such as lithium, may be effective to some degree in people with conditions other than bipolar disorder. That includes conditions such as major depressive disorder, impulse control disorders, or some personality disorders. Psychiatrists may sometimes prescribe bipolar disorder treatments for people believed to have bipolar spectrum disorders. These medications are typically anti-seizure medications or antipsychotic medications. Examples include: Lithium Lamictal (lamotrigine) Depakote (divalproex) Tegretol (carbamazepine) Abilify (aripiprazole) Risperdal (risperidone) In bipolar spectrum conditions, these mood stabilizers are generally used as add-on therapies after treating the main mental condition. However, because these types of medicines have not been as well-studied for conditions other than bipolar I or II disorder, some experts caution against presuming that they will be helpful, and question the appropriateness of their widespread use until appropriate large-scale studies are done to establish their safety and efficacy in non-bipolar conditions. Like other areas of medicine, psychiatry is constantly undergoing changes in the face of new treatments and new ideas. The basic concept of a bipolar spectrum is more than a century old, having been proposed by the original founders of modern psychiatry. It gained new life in the 1970s after a leading psychiatrist proposed classifying mood symptoms as follows: Upper-case " M": Episodes of full-blown mania Lower-case "m": Episodes of mild mania (hypomania) Upper-case " D": Major depressive episodes Lower-case "d": Less-severe symptoms of depression Under this proposed classification, people are described by the combination of their manic and depressive symptoms. This system has not entered mainstream or standard use, however. This past decade has been a period of renewed interest by some psychiatrists in exploring whether the bipolar spectrum may exist as a scientifically valid diagnostic concept. Whether a bipolar spectrum exists and how important it might be continue to be examined by researchers and, meanwhile, debated among psychiatrists.