preparing to be flamed here but had an experience today - friend expecting third child any day, has a 5 yr old and 2.5 yr old. older child struggling at school with letter sounds and friend struggling to cope to give them attention (which is what school say 5 yr old needs).
i was one of 5, all within a year or so of each other - i was never lonely, but it was hectic, quite fraught a lot of the time and a constant struggle for any kind of attention from exhausted (and poor) parents.
when I struggled with my ds after he was born, i was referred to a therapist. they were adamant that in the best interest of the child, it was advisable that a 3 yr gap should be the minimum in order to really nurture your baby. I have two psychotherapist friends who agree and I can't help thinking this is right.