Hi Anya
PIP isn't based on specific conditions, it is based on how the symptoms you have affect your daily living and your mobility as per the specific PIP criteria.
You need to show that you are affected for the majority of the time. So are you in pain for four out of seven days and what does that pain affect you from doing? Does it affect your mobility or your ability to cook, dress yourself etc. The same applies for your depression, you need to look at each question and state what impact it has.
We have a very comprehensive PIP guide. If you look through that, it will give you some idea of how you might answer questions.
www.benefitsandwork.co.uk/help-for-claimants/pip#claims BIS