A tremor is an involuntary movement or shaking of any body part (even your head or voice may be involved). It is often most noticeable in your hands. There are three main types of tremors:

• Resting or static tremors -- occur when your hand or affected body part is at rest.
• Intention tremors -- occur when you are moving your hand or affected body part and disappear at rest.
• Postural tremors -- occur when you are holding your hand or affected body part in a particular position for a period of time.

Tremor - arms or hands

Tremors can happen at any age but tend to be more common in older people.

You can develop a tremor from fatigue, stress, anxiety, or even rage. However, an ongoing tremor that is not associated with a change in your emotional state may be a sign of an underlying medical condition and should be evaluated. You may learn, as many do, that your tremors are perfectly normal, but eliminating medical reasons for the shaking is important.

It is especially important to have tremors evaluated if body parts other than the hands are involved, like your tongue or head, or if you have other types of involuntary movements other than shaking.

Essential tremor is common in older people. Essential tremor is rarely present when the hands are not being used. It becomes most apparent when the affected person is trying to do something, like reaching for an object or writing. It is not caused by an underlying disease.

Another common type of tremor is called familial tremor which, as the name implies, tend to run in families.

Both essential and familial tremors may be suppressed by drinking alcohol. This is a useful fact for making the diagnosis, but alcohol is not a desirable treatment.

Tremors may be caused by:

• Too much coffee or other caffeinated drink
• Excessive alcohol consumption, alcoholism, or alcohol withdrawal
• Stress, anxiety, or fatigue -- these can cause a postural tremor
• Normal aging
• A variety of drugs and prescription medicines
• Low blood sugar
• Parkinson's disease -- this is the classic cause of a resting tremor and is often accompanied by slowness of movement, muscle rigidity, and an abnormal gait
• Multiple sclerosis -- can cause an intention tremor
• Over active thyroid -- can cause a postural tremor

Louis ED. Essential tremor. Lancet Neurol. 2005; 4(2): 100-110.

Louis ED, Ford B, Frucht S, Rabinowitz D, Ottman R. Evidence for familial aggregation of tremor in normal individuals. Neurology. 2001; 57(1): 110-114.