My son, now 5, has so many symptoms of SPD. I have looked into many other "disorders" and such, but have found nothing that fits him except for SPD. However, he was the happiest baby I had (He was my 3rd of my now 4 boys) until he hit about 12-18 months. It was overnight that he went from happy to just grumpy & seemingly miserable and he has not ever recovered. Can SPD start later than at birth?