There are many terms in psychology that can be confusing. Particularly when the concepts can be co-occurring. The difference between dissociation and tonic immobility will be explained below. It is useful to know this difference as it has clinical implications. First I will explain what dissociation is and what tonic immobility is.
What is Dissociation?
Dissociation is a detachment from reality, it is a mental process where a person disconnects from their thoughts, feelings, memories or sense of identity. This is different to psychosis, which is a loss of reality or an experience of a delusional reality.
Dissociation exists on a continuum. An example of the low end may be, where one is not aware of the journey that they took to work, although they arrived safely. “Zoning out”. At the high-end, one has a complete disconnect from surroundings, such as the dissociative disorders (see below). This is where a range of symptoms from memory loss to other identities may occur. Dissociation also occurs in the context of other disorders such as PTSD and BPD. In the case of PTSD dissociation exists on a continuum where at the extreme end there is a complete involvement in re-experiencing trauma.
Disassociation is described in two forms, depersonalisation and derealisation. Depersonalization involves persistent or recurrent experiences of feeling detached from, and as if one were an outside observer of, one’s mental processes or body. The “outer body experience”. Derealization involves persistent or recurrent experiences of unreality of surroundings, “everything is “surreal”.
The range of dissociative disorders includes:
- Dissociative amnesia
- Dissociative fugue
- Depersonalisation disorder
- Dissociative identity disorder
Tonic immobility is not associated with these.
What is Tonic immobility?
Tonic immobility is a temporary state of motor inhibition. It is considered last-ditch defence method, that occurs in situations involving extreme fear. Tonic immobility is an involuntary defensive strategy. The “freeze response”.
Tonic Immobility and Dissociation in PTSD
When someone is in a dissociative state they may be disconnected from their surrounds and from their body, but this does not mean they are in a state of tonic immobility.
The experience of tonic immobility can occur while one is aware of and connected to their surroundings and body. The person is just unable to move.
For example: “I knew he was going to hurt me. I kept backing away, and then there were moments where I froze and then suddenly I was able to move again.”
Alternatively, a person may experience a dissociative state and tonic immobility at the same time.
For example: “I felt the room change it was like I wasn’t there, but I was, I was watching myself and I was paralysed as she was hurting me, I wanted to run but I couldn’t.
Why is it important to know the difference?
There are treatment considerations for dissociation and tonic immobility. For example, Resick et. al (2012) found that Women who endorsed low pre-treatment levels of dissociation responded most efficiently to CPT, whereas women with the highest levels of dissociation, in particular high levels of depersonalization, responded better to CPT with a written account of the trauma (CPT+A). Lima et al 2010 found that tonic immobility has been associated with poor outcomes for pharmacological treatments.
Dissociation may be something that you need to assist clients manage in session. This would be unlikely with tonic immobility, however the meaning of being immobile and the associated powerlessness may well be an important part of the clients experience that needs to be discussed.
Lima, A. A., Fiszman, A., Marques-Portella, C., Mendlowicz, M. V., Coutinho, E. S. F., Maia, D. C. B., . . . Figueira, I. (2010). The impact of tonic immobility reaction on the prognosis of posttraumatic stress disorder. J Psychiatr Res, 44(4), 224-228. doi: 10.1016/j.jpsychires.2009.08.005
Möller, A., Söndergaard, H. P., & Helström, L. (2017). Tonic immobility during sexual assault – a common reaction predicting post-traumatic stress disorder and severe depression. Acta Obstetricia Et Gynecologica Scandinavica, doi:http://dx.doi.org/10.1111/aogs.13174
Resick PA, Suvak MK, Johnides BD, Mitchell KS, Iverson KM. The impact of dissociation on PTSD treatment with cognitive processing therapy. Depress Anxiety. 2012 Aug;29(8):718-30. doi: 10.1002/da.21938. Epub 2012 Mar 30.
Volchan, E., Souza, G. G., Franklin, C. M., Norte, C. E., Rocha-Rego, V., Oliveira, J. M., . . . Figueira, I. (2011). Is there tonic immobility in humans? biological evidence from victims of traumatic stress. Biological Psychology, 88(1), 13-19. doi:http://dx.doi.org/10.1016/j.biopsycho.2011.06.002