This is a mental disorder where people feel the need to check things repeatedly
What is a mental disorder that needs to be check regularly?
Oh I'm sorry I thought you already knew what we were talking about, it is Obsessive–compulsive disorder (OCD) 
Oh!  I have heard of OCD before.  Is it a condition that can be cured?
I doubt that it can be cured because the cause is unknown
What are some of the symptoms of OCD?
Inability to  control either the thoughts or the activities for more than a short period of time.