Letter to Study Participants

Dear Participant,

I am writing as a medical scientist from the USC School of Medicine to ask for your help with an important project called the California Twin Program. Our unit has conducted studies of the causes of chronic disease for nearly thirty years. Among those is a study of 17,000 identical and fraternal twins from all over North America, designed to help us understand why certain people get particular life-threatening diseases, while others, similar in almost all respects, remain protected. This study led us to conclude that we also should get information from all the twins, sick or well, in a specific population. California, because of its size and diversity, is the best place to do this. The state government has supported the program and has helped us locate California-born twins. Your name was among the roughly 150,000 listed. So far, about 20,000 older twins, the majority of those asked, have taken the trouble to participate. Much larger numbers of participants of all ages, both sexes, and all races and ethnicities are needed to ensure success. Assuming that you truly are a twin who was born in California, please help us make this project successful. To express our appreciation in advance, we enclose a sticker designed especially for California twins.

We will shortly send you a booklet with a set of questions. We only ask that you help us by taking the time to mark the answers. They ask about your individual experiences, about the choices you have made in life, and about the differences between your experience and that of your twin. If you have any questions about twins, or diseases in twins, we will try to answer them, and we do plan to make available the results of the survey. Otherwise, participation in the project will not benefit you personally (although most participants seem to enjoy searching their memory to answer questions designed especially for twins). In addition, for those who are interested, we hope that we soon can offer at cost a very inexpensive and very accurate test of zygosity (i.e. a test to tell whether twins are truly identical or fraternal).

There is certainly no cost for participation, except the time it takes to mark your responses, and you will not be asked for money (your cooperation is more important than a charitable gift). All information will be held in complete confidence, including the facts that you are a California native and a twin. No outside persons will have access to your name, or to your answers, without your permission. Results will only be released in statistical form, and no persons or twin pairs will ever be identified. Please help; it will take only about a half-hour of your time and you may withdraw at any time. If convenient, please encourage your twin to participate also. The more twins who participate, especially as pairs, the bigger the impact we can make against the many diseases and health-related problems that reduce the quality of life.

You should receive the booklet in a few weeks. Please fill it out and send it right back. If you are not a twin, still be sure to open the envelope and send the booklet back to us with that message. Then we can promptly cross you off our list so that you will not be disturbed again. If you have any general or confidential questions, we will be happy to answer them by mail (address below), phone (our toll-free number is 888-328-6478), or with our website, (https://twins.usc.edu).

Thank you very, very much for your cooperation.

Sincerely yours,

Thomas Mack M.D., M.P.H.

USC/Norris Comprehensive Cancer Center
1441 Eastlake Ave., MS 44
Los Angeles, CA 90033-0800