I've wondered about it all since I was a little kid. There's very little research out there on the subject unfortunately. What I have read points at a few different reasons for the phenomenon. It's an interesting topic as there seems to be a root cause that seems to be based in early childhood. But there seems to be another group that seems to have just stumbled upon diapers and found they enjoy them. The second begs the question - is there just a repressed attraction that gets the person reintroduced later in life? I suspect that there's a few kinksters out there that have no childhood attachment. They tried a diaper on for whatever reason and found them cool. The BDSM group would probably have a lot of DLs that fall into a group like this. Diapers to them are just another tool of torture to them.
Speaking for myself, I have come to realize that my attraction was formed extremely early in my life. Diapers and particularly plastic pants have been a source of intense desire from as early as I can remember. I've read a lot of posts that folks wonder if it was bedwetting, abuse, etc. that caused us to have the fetish. Finding safety and security from an emotional storm in diapers for these folks is pretty easy for me to understand. My heart goes out to these folks.
But for me it's different. My DL points to an attraction that was formed before I was even consciously thinking. As early as I can remember I have always wanted diapers and plastic pants. They always brought about this giggly, tickly thrill that attracted me like a moth to a light. At the age of 4,5, always and increasing especially as I reached the sexual maturity of puberty.The psychologists believe this is caused by faulty imprinting. Our attraction begins when we find diapers and the related objects and sensations pleasurable and central to our reality. This all happened before we developed a personality. Before I became "me". It had nothing to do with abuse, lack of nurturing or anything related.
Psychologists have found that even newborns are sexual beings. So it's easy for me to see how we innocently get misdirected to the tactile sensations of softness and warmth. For me the touching of plastic over a thick diaper is incredibly enjoyable. I suspect I did this a LOT when I was an infant. Wetting only makes the whole experience more intense. I recall now that the early feelings that diapers brought about in me were the same feelings that sexual arousal brings now. I just simply attached the extra baggage of diapers and rubber pants and the associated experiences to the primal sexual need "to breed".
Added to this is the emotional trauma that life inflicts on all of us. Albeit in varying degrees. We all handle these stressors in different ways though. So for some people to turn to the sanctuary of a time when we were kept safe from a hard world, a time when diapers were an iconic part of that safety makes a lot of sense to me. When life presses too hard on us we wish to return to the comfort of our diapers. The fact that diapers feel so darned nice makes this phenomenon even easier. Diapers have become bonded to us as a means of defending our psyche from the onslaught of daily life.
Where the AB part of DL fits in for me is just a different point on the spectrum of DL. It's probably a point further and deeper into the phenomena. Same thing, only with more whistles and bells added. Both mentally and materially. This is where I'm at. I'm a diaper junky. Always looking to score that ultimate "diaper high". Diapers are a classic addiction for me. I am probably obsessive compulsive and would be diagnosed that by a professional. I found that by gradually adding more and more of the items related to diapers added greatly to my enjoyment. This naturally took me into the "adult baby" aspect of DL completely unintended. It started with a diaper and progressed unconsciously to where I'm now an AB. And yes, it is to a large part sexual in nature as well as comforting. I have the added flaw of enjoying humiliation. Somewhere in my early years I got myself miswired to where humiliation is a sexual pleasure. So this is added to the already existing sexual attraction of "diapers".
So, I see AB/DL totally interrelated and also in the same category of all fetishes. Talking to a shoe fetishist would probably be the same as talking to a DL. Just interchange the word "shoe" for "diaper". The same miswiring that caused us to want diapers probably caused them to want women's shoes....or panties, or whatever...
Well, this is getting long. I hope this helps those who are haunted by the diaper experience like I am. I've come to the place in life where I have shed the heavy guilt of liking diapers. I realize that I got formed innocently as a diaper lover long before there was anything I could do about it. It's as much a part of me as much as my fingers. Just enjoy your diapers. They're a part of you that isn't going to go away any more than your fingers.
You know the ol' saying about life giving you lemonade....Life gave us diapers....lol....