Tremor and disease activity/intensity can worsen in response to fatigue, strong emotions, low blood sugar, cold and heat, caffeine, lithium salts, some antidepressants, and other factors. Typically, the tremor worsens in "performance" situations, such as when writing a cheque for payment at a store or giving a presentation.Parkinsons disease and parkinsonism can also occur simultaneously with ET. The degree of tremor, rigidity, and functional disability did not differ from patients with idiopathic Parkinsons disease. Hand tremor predominated (as it did in Parkinsons disease), and occurred in nearly all cases, followed by head tremor, voice tremor, neck, face, leg, tongue, and trunk tremor. Most other tremors occurred in association with hand tremor. More severe tremors, a lower sleep disorder frequency, and a similar prevalence of other non-motor symptoms also can occur.Walking difficulties in essential tremor are common. About half of patients have associated dystonia, including cervical dystonia, writers cramp, spasmodic dysphonia, and cranial dystonia, and 20% of the patients had associated parkinsonism. Olfactory dysfunction (loss of sense of smell) is common in Parkinsons disease, and has also been reported to occur in patients with essential tremor. A number of patients with essential tremor also exhibit many of the same neuropsychiatric disturbances seen in idiopathic Parkinsons disease.Essential tremor with tremor onset after the age of 65 has been associated with mild cognitive impairment, as well as dementia; although the link between these conditions, if any, is still not understood.Essential tremor has two tremor components,  central and peripheral.
ET is generally progressive in most cases (sometimes rapidly, sometimes very slowly), and can be disabling in severe cases. Epidemiology
ET is one of the most common neurological diseases, with a prevalence around 4% in persons age 40 and older and considerably higher among persons in their 60s, 70s, and 80s, with an estimated 20% of individuals in their 90s and over. Aside from enhanced physiological tremor, it is the most common type of tremor and one of the most commonly observed movement disorders. Society and culture
Actress Katharine Hepburn (1907–2003) had an essential tremor, possibly inherited from her grandfather, that caused her head—and sometimes her hands—to shake. The tremor was noticeable by the time of her performance in the 1979 film The Corn Is Green, when critics mentioned the "palsy that kept her head trembling". Hepburns tremor worsened in her later life.Charles M. Schulz, American cartoonist and creator of the Peanuts comic strip, was affected during the last two decades of his life. West Virginia Senator Robert Byrd also had essential tremor. In 2010, musician Daryl Dragon of The Captain and Tennille was diagnosed with essential tremor, with the condition becoming so severe that Dragon was no longer able to play the keyboards.Director-writer-producer-comedian Adam McKay was diagnosed with essential tremor.Downton Abbey creator Julian Fellowes has the condition, as does the shows character Charlie Carson.In 2022, Matthew Caws of Nada Surf and his son made a PSA called "Living with a Mild Essential Tremor". Research
Harmaline is a widely used model of essential tremor (ET) in rodents.