Back to Health A to Z. Cyclothymia, or cyclothymic disorder, causes mood changes — from feeling low to emotional highs. Cyclothymia has many similarities to bipolar disorder. Most people's symptoms are mild enough that they do not seek mental health treatment, or the emotional highs feel nice, so they do not realise there's anything wrong or want to seek help. But the mood swings can affect daily life, and cause problems with personal and work relationships. People with cyclothymia are at risk of developing bipolar disorder, so it's important to get help before reaching this stage.
Mood disorders - Symptoms and causes - Mayo Clinic
A mood swing is an extreme or rapid change in mood. Such mood swings can play a positive part in promoting problem solving and in producing flexible forward planning. Mood swings can happen any time at any place, varying from the microscopic to the wild oscillations of manic depression ,  so that a continuum can be traced from normal struggles around self-esteem , through cyclothymia , up to a depressive disease. The duration of mood swings also varies. They may last a few hours - ultrarapid - or extend over days - ultradian : clinicians maintain that only when four continuous days of hypomania, or seven days of mania, occur, is a diagnosis of bipolar disorder justified.
When a person feels irritable, small things that would not usually bother them can make them feel annoyed or agitated. The resulting tension can make a person more sensitive to stressful situations. Irritability is a common emotion. Many factors can cause or contribute to irritability, including life stress , a lack of sleep, low blood sugar levels, and hormonal changes.
On the other hand, you may have a medical condition if you switch from extremely happy to extremely depressed on a regular basis. If you have serious and frequent shifts in mood, you should tell your doctor about them. Some causes of rapid changes in behavior can be related to mental health, hormones, substance use, or other health conditions. But if your behavior is unpredictable for a number of days or longer, it may be a sign of something more serious. You may feel grumpy one minute and happy the next.