I can't remember where I read it as it's been close to 10 years ago. I have what's called sleep starts where I jerk as I'm going to sleep which is why I was researching this, and why this stat stuck in my head. I think I was research tardive dyskinesia as a family member was sure that was what I have--I don't, it's sleep starts.

Do some research and see what you come up with. Google the name of your med with the term 'side-effects, myoclonus, tardive dyskinesia' and see what you come up with.

Here's an article that I found by googling 'psych meds, movement disorders.' Below is a very interesting quote that shows the magnitude of the problem.

"What causes tardive dyskinesia and tardive dystonia?

The exact ways in which psychiatric medications cause tardive dyskinesia and tardive dystonia is still under debate. However, there is no doubt that traditional anti-psychotic drugs cause these disorders in some people who use them. Examples of medications which cause these movement disorders include Thorazine, Stelazine, Haldol, and Prolixin. The relatively new drug Zyprexa (Olanzapine) has been found to cause TD. The risk of TD and other movement disorders cannot be ruled out for people using Risperdal (risperidone). At this time no cases of tardive dyskinesia have been reported for people using Clozaril (clozapine).

Who will get tardive dyskinesia and tardive dystonia?Although the statistics vary somewhat, there is no doubt that a significant percentage of people who use neuroleptic or "anti-psychotic" medications will develop a movement disorder caused by those medications. Some studies estimate there are already 250,000-400,000 people in the United States who have tardive dyskinesia. Different studies quote different rates of tardive dyskinesia ranging from 15%-20% for people using the drugs for more than three years, to as much as 40%-70% of elderly people with long term use. The rates at which tardive dystonia occurs has not been reliably established.

These statistics tell us that although many people do develop movement disorders as a result of using psychiatric medications, some people do not. Unfortunately there is no way to predict who will and will not develop TD. What seems certain is this: the longer we use certain neuroleptic or antipsychotic medications, the greater our chance of developing tardive dyskinesia and/or tardive dystonia."

Tardive Dyskinesia and Tardive Dystonia: where you can turn for help - NEC Article