Age, Sex and Other Predispositions

Although acute dystonia can occur at any age, it is 2-3 times more common in patients under 35 and there is a linear decrease with age. In patients under 50 years of age, the incidence in men is twice that in women. The reaction rate in the over 50s is the same for men and women.

Other predispositions

These include family history of acute dystonic reactions or previous history of dystonia (estimated relative risk = 6), alcohol abuse and cocaine use (estimated relative risk = 3-4). Emotional stress, fatigue, viral infections, hypocalcaemia, hypoparathyroidism and dehydration also increase risk.

There is no clear evidence to determine whether the nature of the psychiatric illness e.g. bipolar disorder, depression or schizophrenia affects the incidence of dystonic reactions. Nor is there any evidence implicating any effect of race.