The Theory of Structural Dissociation²²

When talking about DID/OSDD, the phrase ‘Theory of Structural Dissociation’ may be thrown around quite often. The Theory of Structural Dissociation (sometimes abbreviated ToSD) comes from the 2006 book The Haunted Self: Structural Dissociation and the Treatment of Chronic Traumatization. The Theory of Structural Dissociation is a theory of how dissociation is used to maintain a lack of cohesion in one person’s mind. It is a useful tool to understand how dissociation may affect someone with trauma.

The Theory of Structural Dissociation posits that there are a cluster of action systems that lead a human being to act, which are emotional systems, functional systems, and defensive systems. Functional systems take care of functional, everyday life tasks, while emotional systems focus on the emotions that someone may feel from day to day. Defensive systems are commonly thought of as the ‘fight, flight, or freeze’ responses that a human being has when faced with danger.

When a human being uses dissociation as a coping mechanism to an excessive degree, they too may develop a series of action systems; namely, the ANP (Apparently Normal Part) and the EP (Emotional Part). The EP essentially holds the trauma that an individual is going through and primarily acts upon the emotional system that prompts them to react as if the trauma was still ongoing. With the trauma dissociated from the ANP, the ANP can continue to function as if everything was normal, using numbing and amnesia to further detach themselves from the trauma that affects the EP.

There are three levels of structural dissociation: primary, secondary, and tertiary. The primary level of structural dissociation involves only one EP and one ANP. The ANP is often considered to be in control most of the time, while the EP may surface during dire moments such as flashbacks. PTSD falls under the categorization of the primary level of structural dissociation.

The secondary level of structural dissociation can vary with the amount of EPs, but still only contains one ANP. BPD (Borderline Personality Disorder), DDNOS (Dissociative Disorder Not Otherwise Specified (No longer in use as a diagnosis)), and OSDD (not included in the original version of The Haunted Self) fall under the categorization of the secondary level.

The tertiary level of structural dissociation has a varying amount of both EPs and ANPs. DID falls under the tertiary level of structural dissociation. It is posited that the alters present in DID are comprised of varying EP and ANP roles.

While the Theory of Structural Dissociation is useful to understanding trauma and dissociation, it is important to note that it is only one way of understanding systems and is not the end-all-be-all of diagnostics. The distinction between EP and ANP can be very helpful in understanding why some parts act the way that they do, but it is far fron necessary to attempt to label every part with either the role ‘ANP’ or ‘EP’. The Theory of Structural Dissociation was also written before the diagnostic label of OSDD came out in the DSM-5, so this theory is not used as a diagnostic benchmark for distinguishing between OSDD or DID. An OSDD system may have multiple ANPs, while a DID system may only have one EP and one ANP. The Theory of Structural Dissociation only provides general classifications, not hard-set rules.