Clinical trials are research studies that look at new ways to prevent, detect, or treat diseases and conditions, including OCD. During clinical trials, investigated treatments might be new drugs or new combinations of drugs, new surgical procedures or devices, or new ways to use existing treatments. The goal of clinical trials is to determine if a new test or treatment works and is safe. Although individual participants may benefit from being part of a clinical trial, participants should be aware that the primary purpose of a clinical trial is to gain new scientific knowledge so that others may be better helped in the future.
Some common compulsions include hand washing, cleaning, checking things (., locks on doors), repeating actions (., turning on and off switches), ordering items in a certain way, and requesting reassurance.  Compulsions are different from tics (such as touching, tapping, rubbing or blinking)  and stereotyped movements (such as head banging, body rocking or self-biting), which usually aren't as complex and aren't precipitated by obsessions.  It can sometimes be difficult to tell the difference between compulsions and complex tics.  About 10% to 40% of individuals with OCD also have a lifetime tic disorder. 
Similar to obsessions, not all repetitive behaviors or “rituals” are compulsions. You have to look at the function and the context of the behavior. For example, bedtime routines, religious practices, and learning a new skill all involve some level of repeating an activity over and over again, but are usually a positive and functional part of daily life. Behaviors depend on the context. Arranging and ordering books for eight hours a day isn’t a compulsion if the person works in a library. Similarly, you may have “compulsive” behaviors that wouldn’t fall under OCD, if you are just a stickler for details or like to have things neatly arranged. In this case, “compulsive” refers to a personality trait or something about yourself that you actually prefer or like. In most cases, individuals with OCD feel driven to engage in compulsive behavior and would rather not have to do these time consuming and many times torturous acts. In OCD, compulsive behavior is done with the intention of trying to escape or reduce anxiety or the presence of obsessions.