Both have been detailed and proposed for DSM inclusion. Developmental trauma (DTD) easily had the vote then somehow didn't show up. There are all kinds of practical and political issues, I'm sure. Bessel van der Kolk seems to hint at this when he discusses the money that could be saved by adequately framing a child's issues versus diagnosing them with a long list of symptoms-related disorders (but then I suppose blame is cast on the parents more easily than the child, and what does that mean for the whole system, etc??? I think it's highly imperfect and just plain effed up sometimes)
I do think there are important differences, though many people who would have DTD would also have CPTSD, especially if the primary trauma is within the family. There are some distinct features, such as developmental trauma more likely results in total disconnection and avoidance of relationships, whereas complex trauma can more often result in wavering between idolizing and fearing the abuser/captor...and also repeatedly searching for a rescuer. All of this could certainly be studied further.
Developmental trauma (or proposed DTD, described by Bessel van der Kolk and Laurence Heller): Very early abuse, shock trauma, and/or attachment trauma. Major early medical issues and abuse are good examples because they disrupt both physical safety and development of safe attachments. Symptoms are "global", as in having potential to effect nearly all body systems, but most noticeable in areas of nervous system dysregulation and relationships/connection. The main issue is that the traumas and/or failed attachment is responsible for the nervous system not even getting regulated from the beginning. So even if the shock or danger passes, the protective responses or disconnection are deep patterns.
Complex trauma (or CPTSD, described most fully by Judith Herman, but also Bessel van der Kolk): Multiple or chronic trauma, such as hostage situations or living in a consistently abusive house as a child. So it's not that the nervous system is set off track from day one, necessarily, but that the chronic trauma dysregulates one far enough that they can end up stuck on a somewhat globalized level, like DTD. Various forms of dissociation common in both because the being stuck or trapped with ongoing threat makes anything else almost impossible. Nervous system shutdown is a way of surviving through it.
I think if anything could be added to DSM, CPTSD could cover both. Developmental trauma does not describe hostage situations or later childhood or adulthood multiple traumas.
My traumas would be described as both (physical, medical, attachment, sexual trauma...from age 0 into early adulthood, but not all chronic or continuous). Adult traumas tossed me over the edge into suicide attempts, but what I'm working on (where I'm most stuck) is the early trauma. My therapist calls my stuff "globalized high intensity complex trauma" (globalized high intensity activation is a term used by Heller and SE people). I don't look to the DSM as our bible of psych language.
Diagnosis is important (especially when we do have a diagnosis for PTSD and many people want to self-diagnose because they feel very horrible after a break-up or bad drug trip). But nothing in DSM describes developmental trauma right now. I have not been diagnosed with an attachment disorder, personality disorder, or major dissociative disorder, but have traits of all of them, some very strong...as well as some symptoms that seem autism spectrum, bipolar, and ADHD (I have adult-diagnosed PSTD, which doesn't explain all of it very well and the therapy was NOT helpful). Hand me over to a dumbshit clinician and I could have a list of 10+ disorders and feel really hopeless. I'm sure there is a separate diagnosis for self harm by now too...so I'd have that too, along with anorexia and "SUDS" or whatever they'd want to call alcoholism and dependence on cocktails of uppers and downers. And sleep disorder, major depression, panic disorder, and chronic pain. For me, these are all symptoms of the nervous system dysregulation and fierce shutdown and self protection. Just calling it all complex trauma makes me feel less ashamed for being f*cked up on so many levels. And so far I've gained a lot more in cutting through very old patterns by working with a therapist who treats it all as complex trauma.
I don't even know yet if the more important distinction for me would be "developmental trauma" or "complex". But it seems fair to say you could have one or the other (I think of mute or walled-off kids who have a loving, protective family but had some really difficult shock traumas in early childhood...or the complex types who had chronic trauma after having a decent early childhood and healthy regulation to start with, but it fell off the tracks).
That being said, there are many trauma specialists who recognize developmental and complex traumas and understand some of the challenges for therapy, as well as some of the newer methods which work more directly with disconnection, dissociation, and chronic nervous system dysregulation. There is often overlap, but there is much written about both as having some distinct features. And need for continued study.
