Well, it certain will affect your CV! But as someone who is right now working in the audit field, if you really cannot withstand the long working hours and stress, my advice is find another job first before quitting. The economy is not very good right now and i pretty sure you can see through the accounting figures from your client's accounts.
It is not very difficult to get fresh graudates jobs now because the demands are still there. Perhaps the career progression might be slight slower in commercial, but it all depends on what you want to achieve in life.
Some can tahan up to 3-4 years and be promoted to Assistant Managers, then ciao to commercial, they are doing really fine!
Quit a job after only 5 months?