Best way to set up database tables
You have no need to add a "modules" field to your main/users table.  Just JOIN on the tables -- that's what Relational Databases are for.  INNER or OUTER joins should be used depending on your needs.  

For example, this will return a user with their conditions.  If the user doesn't have any conditions, it will return NULL for those fields, but it will still return the user:

SELECT * 
FROM User U
   LEFT JOIN Conditions C ON U.Id = C.User_ID


Good visual representation of joins