Are you looking for specific mental illnesses or just any mental illness?  Because according to the World Health Organization approximately 20-25 percent of the population will suffer from a mental illness at some point in their life.  Therefore, the number of children living with a parent with a mental illness would probably be quite high.  

I'm looking for specific numbers for any mental illness. The NIMH has number for how many adults live with both any mental illness and serious mental illness. And its broken down into age range so I can sort of extrapolate how many are in the age range where they might be parents. However, I'm trying to find prevalence numbers that looks at this issues from the other end - how many children live with parents with mental illness. I have only been able to find numbers for Norway and the UK so far. 

Dear Kelli

Your question is very interesting. Can you share the publications from the UK and Norway?

Kelli, I agree with Ashley, most of us at some time have an emotional disorder strong enough to be classified as one.  I think you are looking for those officially diagnosed that would leave most of us undiagnosed out of your  interesting study.  The age you look at is important also, for in the 70's etc a mental illness would be more denied and hide.

If you are running for public office (etc.) they can check your health records and see that you have been treated for mental illness.  The privacy act helps.  Good luck. 

I agree with

Did you see:

Nicholson, J., Biebel, K., Williams, V. F., & Katz-Leavy, J. (2004). Prevalence of parenthood    in adults with mental illness: Implications for state and federal policy, programs, and     providers. In R. W.Manderscheid & M. J.Henderson (Eds.), Mental health, United   States, 2002. DHHS Pub No. (SMA) 3938 (pp. 120– 137). Rockville, MD: Substance           Abuse and Mental Health Services Administration.

Thanks Peter. I do have that reference. It giives the prevalence of parenthood in those with mental illness. I do not believe it has the prevalence of having a parent with mental illness for children. But I will look again to make sure.