Kalhbaum was the first to recognize that people with cyclothymia often do not seek help for the disorder due to its milder symptoms.Cyclothymia has been conceptualized in a variety of ways, including as a subtype of bipolar disorder, a temperament, a personality trait, and a personality disorder. There is also an argument that cyclothymia should be considered a neurodevelopmental disorder. The two defining features of the disorder, according to DSM-5, are the presence of depressive and hypomanic symptoms, not meeting the threshold for a depressive or hypomanic episode. Cyclothymia is also classified as a subtype of bipolar disorder in DSM-5, but some researchers disagree with this classification and argue that it should be primarily defined as an exaggeration of mood and emotional instability. In the past, cyclothymia has been conceptualized to include other characteristics in addition to the flux between depression and hypomania, such as mood reactivity, impulsivity, and anxiety. Epidemiology
Cyclothymia, known today as Cyclothymic Disorder, tends to be underdiagnosed due to its low intensity. The exact rates for Cyclothymia have not been widely studied. Some studies estimate that between 5 and 8% are affected at some point in their life whereas other studies suggest a rate ranging from 0.4 to 2.5%.Males appear to be affected equally often, though women are more likely to receive treatment. Cyclothymia is diagnosed in around fifty percent of people with depression who are evaluated in psychiatric outpatient settings. Etymology
Cyclothymia is derived from the Greek word κυκλοθυμία (from κῦκλος, kyklos, "circle" and θυμός, thymos, "mood, emotion").
Hair loss may be present in the family, highlighting genetic causes. Causes
Causes of noncicatricial alopecia can be separated based on focal or diffuse hair loss:Diffuse:

Androgenetic alopecia: androgenic DHT leads to catagenic miniaturization of hair follicles. Diffuse alopecia areata: diffuse autoimmune destruction of hair follicles
Alopecia totalis: unknown but thought to be autoimmune
Telogen effluvium: emotional or physiologic stress
Anagen effluvium: cancer treatments such as radiation and alkylating agents
Dermatopathia pigmentosa reticularis: genetic autosomal dominant conditionFocal:

Alopecia areata: autoimmune destruction of hair follicles
Tinea capitis: fungal infection
Traction alopecia: pulling force applied to hair
Trichotillomania (Trichotillosis)

Diagnosis
There are a number of conditions that may cause non scarring hair loss and the first step is to determine the pattern: focal or diffuse. The next step is to identify if the hair loss is scarring or non scarring. A history and physical examination is necessary as this will provide clues to the ultimate diagnosis. It is essential to ask about the onset, observed pattern, hairstyles, family history, diet, and social history.Diffuse:

Androgenetic alopecia: history of gradual thinning of hair and characteristic pattern. Males start to lose hair in the front and temples while females lose hair at the top of the head
Diffuse alopecia areata: exclamation point hairs
Alopecia totalis: concomitant loss of facial and skull hair
Telogen effluvium: history of emotional or physiologic stress
Anagen effluvium: history cancer treatments such as radiation and alkylating agents
Dermatopathia pigmentosa reticularis: genetic autosomal dominant conditionFocal:

Alopecia areata: smooth and round lesions
Tinea capitis: black dots with broken hair strands, may see red, scaly lesions and swollen lymph nodes on the back of head.