I've only just made the mental link for myself but my PND is under control in the day and suddenly worse by the evening.
I suddenly feel like I can't cope with my son: I feel overwhelmingly exhausted, irritable and can't face doing bedtime (he is difficult to get into bed anyway, doesn't go in his own cot most of the time, and is a fussy feeder). But I just feel helpless and useless in the evenings!
Anyone else?!