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Cyclothymia, also called cyclothymic disorder, is a type of chronic mood disorder widely considered to be a milder or subthreshold form of bipolar disorder. Cyclothymia is characterized by numerous mood disturbances, with periods of hypomanic symptoms alternating with periods of mild or moderate depression.
An individual with cyclothymia may feel stable at a baseline level but experience noticeable shifts to an emotional high during hypomanic episodes with symptoms similar to those of mania but less severe, and emotional lows involving depressive symptoms that do not meet the criteria for a major depressive episode. To meet the diagnostic criteria for cyclothymia a person must experience this alternating pattern of emotional highs and lows for a period of at least two years with no more than two consecutive symptom free months. For children and adolescents the duration must be at least one year.
While diagnosis of cyclothymia is becoming more common, it is not as frequent as that of bipolar disorder. Diagnosis of cyclothymia presupposes absence of a major depressive episode, manic episode or mixed episode, which would qualify the individual for diagnosis of another mood disorder. When such episodes manifest after an initial diagnosis of cyclothymia, the individual may qualify for a diagnosis of bipolar I or bipolar II disorder. Although estimates vary greatly, 15–50% of cases of cyclothymia later fit the diagnostic criteria for bipolar I and/or bipolar II disorder (resulting in a diagnosis of bipolar I or II with cyclothymic features).
Although the emotional highs and lows of cyclothymia are less extreme than those of bipolar disorder, the symptomatology, longitudinal course, family history and treatment response of cyclothymia are consistent with bipolar spectrum. Lifetime prevalence of cyclothymic disorder is 0.4–1%. Frequency appears similar in men and women, though women more often seek treatment. Unlike during episodes of bipolar I disorder, people with cyclothymia are more likely to be either somewhat or fully productive, and sometimes even hyper-productive.
Cyclothymia is similar to bipolar II disorder in that it presents itself in signature hypomanic episodes. Because hypomania is often associated with exceptionally creative, outgoing, and high-functioning behavior, both conditions are often undiagnosed. As with most of the disorders in the bipolar spectrum, it is the depressive phase that leads most sufferers to get help.
Cyclothymia is characterized by short cycles of depression and hypomania that fail to meet the sustained duration criterion for major affective syndromes (e.g. bipolar disorder, major depressive disorder).
Depressive/dysthymic episodes. Symptoms of the depressive/dysthymic phase include difficulty making decisions, problems concentrating, poor memory recall, guilt, self-criticism, low self-esteem, pessimism, self-destructive thinking, constant sadness, apathy, hopelessness, helplessness and irritability. Also common are quick temper, poor judgment, lack of motivation, social withdrawal, appetite change, lack of sexual desire, self-neglect, fatigue, and insomnia.
Hypomanic episodes. Symptoms of the hypomanic episode include unusually good mood or cheerfulness (euphoria), extreme optimism, inflated self-esteem, rapid speech, racing thoughts, aggressive or hostile behavior, lack of consideration for others, agitation, massively increased physical activity, risky behavior, spending sprees, increased drive to perform or achieve goals, increased sexual drive, decreased need for sleep, tendency to be easily distracted, and inability to concentrate.
The following are the revised criteria for a diagnosis of cyclothymic disorder (DSM-IV-TR 301.13) from the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR):
The DSM-IV-TR notes that the mood disturbance must be not severe enough to constitute a full fledged manic or major Depressive episodes. The diagnosis requires that there be periods of both hypomania and depression and periods of normal mood not last longer than 2 months.
The DSM-IV-TR also notes that some clinicians believe that borderline personality disorder is really cyclothymic disorder in disguise.
Diagnosis of cyclothymia is difficult for a number of reasons. The depressive/dysthymic episode of cyclothymia is also a diagnostic feature of many disorders, including adjustment disorders, personality disorders, psychotic disorders, and other mood disorders. Since depression can be triggered or exacerbated by life events and circumstances, the diagnosing clinician must determine when it is an acceptable response and when it is pathological.
Symptoms described in the hypomanic episode are also commonly associated with ADHD, such as increased energy, distractibility and impulsive or risk seeking behavior. This is of particular concern in child psychiatry because symptoms, especially hyperactivity, may be counted twice toward both disorders or may inflate the prevalence of ADHD. While childhood ADHD often presents with hyperactivity, Adult ADHD often does not. The unstable lifestyle often found both in ADHD sufferers and in those with cyclothymia can cause problems for differential diagnosis. Important distinguishing factors include that ADHD is characterized mainly by problems with concentration and memory, while cyclothymia mainly by periods of elevated self-confidence and elation.
Whether subtypes of bipolar disorders such as cyclothymia truly represent separate disorders or are part of a unique bipolar spectrum is still debated in research. Cyclothymia is typically not described in research studies or diagnosed in clinical settings, making it less recognizable and less understood by professionals. This absence of cyclothymia in research and clinical settings suggest that cyclothymia is either being diagnosed as another mood disorder or as a non-affective psychiatric disorder or not coming to scientific or clinical attention  due to a lack of diagnostic clarity or because the nature of Cyclothymia is still highly contested. Additionally, the current diagnostic criteria for cyclothymia emphasizes that symptoms are persistent, which suggests that they are enduring traits rather than a psychological state, thus, it has been argued that it should be diagnosed as a personality disorder. Since the symptoms tend to overlap with personality disorders, the validity and distinction between these two diagnostic categories has been debated.
Lastly, the tendency of cyclothymia to be comorbid with other psychiatric disorders makes diagnosis difficult. These issues prevent consensus on the definition of cyclothymia and its relationship with other psychiatric disorders among researchers and clinicians. This lack of consensus on an operational definition and symptom presentation is especially pronounced with children and adolescents because the diagnostic criteria has not been adequately adapted to take into account their developmental level. However, there has been a shift from categorical models of bipolar related disorders toward a dimensional model, which is intended to address some of these issues.
This disorder is common in the relatives of patients with bipolar disorder, and some individuals with cyclothymia eventually develop bipolar disorder themselves. It may persist throughout adult life, cease temporarily or permanently, or develop into more severe mood swings, meeting the criteria for bipolar disorder or recurrent depressive disorder in some cases.
The exact cause of cyclothymia is unknown. It is known that major depression, bipolar disorder, and cyclothymia often occur together within families. There may be a genetic component to cyclothymia: In one study, it was found that an individual is 2–3 times more likely to have the disorder if an identical twin is affected.
The use of Lithium and Quetiapine (Seroquel) have both shown to be particularly valuable, though several other medications of the anticonvulsants and atypical antipsychotics classes may also be helpful.  The use of antidepressants as monotherapy typically worsens cyclothymia and can induce mood switching, cycle acceleration, mixed states and prolonged treatment resistance.