My son had terrible colic and I definitely had post-natal depression – but I'm not sure that it was my depression or style of parenting that caused the colic – since his dad, who was much more confident than me, got exhausted by the crying as well. Interestingly, his dad and his dad's siblings all had colic when they were babies too.
It definitely didn't help though that I was inexperienced, totally lacking in confidence and scared stiff everytime he started crying because I couldn't seem to stop it. I guess it was a vicious circle – I tensed up and he probably sensed my anxiety and cried all the more!
I don't understand why more research isn't done about colic since it's so distressing for both parents and baby. I'm not sure how I would cope if put in the same situation again – day by day I guess.