Understanding Obsessive-Compulsive Disorder (OCD) in Veterans: Comparing Veterans with Post-Traumatic Stress Disorder (PTSD) and Complex-PTSD

Mental health problems among ex-Service personnel are often complex, with many experiencing more than one condition at the same time. The latest version of the International Classification of Diseases (ICD-11) now separates post-traumatic stress disorder (PTSD) from complex post-traumatic stress disorder (CPTSD) [1]. This distinction highlights the need to better understand the different ways these two conditions influence people. One area that is still unclear is how obsessive-compulsive disorder (OCD) might relate to PTSD and CPTSD differently. As such, new research published in April 2025, by researchers at Combat Stress, explored this in a national group of UK ex-Service personnel receiving care [2]. Using data from 428 ex-Service personnel, the study examined different mental health symptoms, military experiences, and well-being to compare the level of OCD symptoms in those with probable PTSD and those with probable CPTSD. This spotlight explains how the research was carried out, what the findings were, and what these findings may mean for future support or treatment.

Understanding the Potential Link Between OCD and PTSD

OCD is a mental health condition characterised by obsessive thoughts and/or compulsive behaviours [3]. OCD often occurs alongside other mental health conditions, and people may be less likely to respond to treatment when more than one condition is present [4,5]. Because of this, it is important to explore other conditions that may occur alongside OCD and understand how they may influence how OCD shows up and how it’s treated. OCD is considerably more common among people with PTSD [6], a mental health condition that can develop after traumatic events and is characterised by reliving aspects of the trauma, avoiding reminders, and symptoms of heightened arousal [3]. The increased co-occurrence of PTSD and OCD may be due to similarities in their symptoms. For example, both conditions involve repeated intrusive thoughts and avoidance behaviour that influence functioning and are driven by the need to avoid any cue, object, or place that may cause distress [3]. Because PTSD and OCD often occur together, it is important to understand how these conditions interact so that treatment can be better tailored to people’s needs.

Understanding the Potential Link Between OCD and CPTSD

With CPTSD recognised as a distinct condition from PTSD in the 2018 International Classification of Diseases [1], there is a need to explore how it may be linked to OCD differently from PTSD. CPTSD includes all PTSD symptoms in addition to another set of symptoms involving difficulties with emotions, identity, and relationships [7]. This additional group of symptoms are called disturbances in self-organisation (DSO). As CPTSD is a relatively new diagnosis, research is still developing. However, previous studies highlight how CPTSD may be just as common, and if not, more common than PTSD in ex-Service personnel [8,9]. As PTSD and CPTSD are high in ex-Service personnel, exploring the potential co-occurrence of OCD is particularly important. To date, no study has yet explored whether the additional symptoms (DSO symptoms) that distinguish CPTSD from PTSD might play an important role in influencing OCD severity. Notably, prior research has illustrated how OCD may interfere with a person’s sense of who they are and relationship difficulties [10,11,12], both of which are related to the additional symptoms in CPTSD. Although findings such as these do not support a link between OCD and the DSO symptoms in CPTSD, they illustrate how OCD may influence characteristics found in DSO. This means that the additional symptoms seen in CPTSD, such as difficulties with emotions and relationships, may be linked to OCD symptoms. However, more research was needed to explore how OCD might relate to PTSD and CPTSD differently.

Aim of the study

The study had two main aims:

• To explore the differences in OCD severity between probable PTSD and probable CPTSD.
• To explore which symptoms specifically might be related to OCD, by examining whether OCD severity was linked to both the PTSD symptoms and the DSO symptoms in CPTSD.

How was the research carried out?

This study used data that had already been collected by Combat Stress, a UK charity that provides support for ex-Service personnel. The data came from a large survey, called the Patient Needs Survey, which asked a group of treatment-seeking ex-Service personnel about their health and well-being. Ex-Service personnel were asked to take part if they: (1) had received support from Combat Stress within the last year, (2) agreed to be contacted about research, and (3) provided an email address. In total, 428 ex-Service personnel completed the survey. For this study, only those who completed the survey sections related to OCD, PTSD, and CPTSD were included. Participants were placed into three groups: (1) probable PTSD, (2) probable CPTSD, and (3) no PTSD.

Key findings

Of the 428 ex-Service personnel who completed the initial Patient Needs Survey, 315 answered the questions relevant to this study. Of these, 21 were identified as having probable PTSD, 197 as having probable CPTSD, and 97 showed no sign of PTSD.

Differences in OCD symptoms between groups

The findings of the current study showed that OCD symptoms differed across all three groups (PTSD, CPTSD, and no PTSD). The results indicated that:

• For ex-Service personnel with probable PTSD (but not CPTSD), PTSD symptoms did not explain differences in OCD symptoms.
• For ex-Service personnel with probable CPTSD, as CPTSD symptoms increased, OCD symptoms also increased.

OCD severity and CPTSD symptoms

For ex-Service personnel with probable CPTSD, both PTSD symptoms and the additional symptoms of CPTSD (DSO symptoms) were linked to OCD severity when looked at separately. Thus, as these symptoms increased, OCD severity increased. However, when both symptom groups (PTSD symptoms and DSO symptoms) were looked at together, only the DSO symptoms (difficulties with emotions, self-concept, and relationships) still predicted OCD severity. PTSD symptoms alone did not predict OCD severity after considering the additional CPTSD symptoms (DSO symptoms).

Conclusion

This study provides insight into how OCD severity may differ in ex-Service personnel with probable PTSD and probable CPTSD. This adds needed evidence as no research had previously explored the difference in OCD severity between individuals with PTSD and CPTSD. Thus, the current study provides novel findings. Although the link between PTSD and OCD could not be confirmed due to the small sample size, findings highlight the importance of recognising CPTSD as a distinct diagnosis when planning treatment. Overall, this study shows that the relationship between OCD and trauma-related disorders in ex-Service personnel is complex, and further research with larger samples is needed to better understand this link and improve support.t

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

If you have any questions about the report, you can get in touch using the study email address: [email protected]

You can access the full report link 

Many thanks to Phoebe Howlett from Combat Stress for writing this Research Spotlight.

References

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