There are different studies of course. The best one was a student's PhD discertation in California that conducted a alcohol and the affect of it on dreams.

The person had people drink alcohol and then sleep the whole night, and then when the people woke up they recorded their dreams. Now, you only remember the dreams that occurred most recently to waking up, so after that long you're not under the influence. So, you have to really watch if the study you're doing is going to actually...have results that tell anything.