In some people, body tremors develop due to a condition that affects the nervous system, such as liver failure, stroke, multiple sclerosis, alcoholism or Parkinson's disease. Mercury poisoning, arsenic poisoning, antidepressants or drugs containing lithium can also cause tremors, according to WebMD.
Nervous system disorders normally impact parts of the brain that control muscle movements in certain areas of the body, including the head, hands, arms, body or legs. Certain movements or postures trigger some tremors, and others might develop due to stress or physical exhaustion, explains the National Institute of Neurological Disorders and Stroke. Some forms of uncontrollable shaking are hereditary and have no known cause.
Tremors affect women and men equally, and although they develop at any age, they usually occur in middle-aged and elderly people. Essential tremors are the most common cause of uncontrollable shaking and generally occur during some form of movement, such as pointing at or lifting an object, notes WebMD. Since there are many possible reasons for uncontrollable shaking, doctors often perform a neurological exam to determine the underlying cause. During exams, doctors normally assess a patient's motor skills, sensory skills and nerve function to determine any limitations, according to the National Institute of Neurological Disorders and Stroke. An electromyogram might be used to diagnose any severe nerve or muscle problems.