Cyclothymia is a mood disorder in which the client displays the characteristic ups and downs (depressions and euphorias) of Bipolar Disorder, to a much lower extent, to the point of not qualifying for a diagnosis of Bipolar Disorder. These symptoms must last for a period of at least two years, with no period longer than 2 months in which they have been at a normal state, and no mixed episodes may have occurred.

The age of onset of Cyclothymia is generally in early adulthood, and is gradual, so it is difficult to pinpoint the exact time of onset. The alternating ups and downs may fluctuate in hours, weeks or months. Times of normal emotions may last for up to 2 months. These clients are not as disabled as those suffering from bipolar disorder, and can generally act in social and work situations, although not at full capacity.

A persistent instability of mood, involving numerous periods of mild depression and mild elation. This instability usually develops early in adult life and pursues a chronic course, although at times the mood may be normal and stable for months at a time. The mood swings are usually perceived by the individual as being unrelated to life events. The diagnosis is difficult to establish without a prolonged period of observation or an unusually good account of the individual's past behaviour. Because the mood swings are relatively mild and the periods of mood elevation may be enjoyable, cyclothymia frequently fails to come to medical attention. In some cases this may be because the mood change, although present, is less prominent than cyclical changes in activity, self-confidence, sociability, or appetitive behaviour. If required, age of onset may be specified as early (in late teenage or the twenties) or late.

from another site:

Less severe hypomanic and mini-depressive periods follow an irregular course, with each period lasting a few days. Cyclothymic disorder is commonly a precursor of bipolar II disorder. But it can also occur as extreme moodiness without being complicated by major mood disorders. In such cases, brief cycles of retarded depression accompanied by low self-confidence and increased sleep alternate with elation or increased enthusiasm and shortened sleep. In another form, low-grade depressive features predominate; the bipolar tendency is shown primarily by how easily elation or irritability is induced by antidepressants.

Although cyclothymic and chronic hypomanic dispositions contribute to success in business, leadership, achievement, and artistic creativity in some persons, they more often have serious detrimental interpersonal and social sequelae. Cyclothymic instability is particularly likely to be manifested in an uneven work and schooling history; impulsive, frequent changes of residence; repeated romantic or marital breakups; and an episodic pattern of alcohol and drug abuse. Treatment Patients should be taught how to live with the extremes of their temperamental inclinations, although living with cyclothymic disorder is not easy because of the resulting stormy interpersonal relations. Jobs with flexible hours are preferred. Patients with artistic inclinations should be encouraged to pursue such careers because the excesses and fragility of cyclothymia are better tolerated in such circles. The decision to use a mood stabilizer depends on the balance between the functional impairment produced by unpredictable mood swings and the social benefits or creative spurts the patient may receive from hypomanic swings.

from another site:

It may persist throughout adult life, cease temporarily or permanently, or develop into more severe mood swings meeting the criteria for bipolar affective disorder or recurrent depressive disorder.

FROM ANOTHER SITE:

Hypomanic Episode:

A distinct period of persistently elevated, expansive, or irritable mood, lasting throughout at least 4 days, that is clearly different from the usual nondepressed mood.

During the period of mood disturbance, three (or more) of the following symptoms have persisted (four if the mood is only irritable) and have been present to a significant degree:

inflated self-esteem or grandiosity
decreased need for sleep (e.g., feels rested after only 3 hours of sleep)
more talkative than usual or pressure to keep talking
flight of ideas or subjective experience that thoughts are racing
distractibility (i.e., attention too easily drawn to unimportant or irrelevant external stimuli)
increase in goal-directed activity (either socially, at work or school, or sexually) or psychomotor agitation
excessive involvement in pleasurable activities that have a high potential for painful consequences (e.g., the person engages in unrestrained buying sprees, sexual indiscretions, or foolish business investments)

The episode is associated with an unequivocal change in functioning that is uncharacteristic of the person when not symptomatic.

The disturbance in mood and the change in functioning are observable by others.

The episode is not severe enough to cause marked impairment in social or occupational functioning, or to necessitate hospitalization, and there are no psychotic features.