Introduction

Several studies indicate that posttraumatic stress disorder (PTSD) is more prevalent in Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) Veterans than the general U.S. population. PTSD leads to substantial personal societal costs – increased likelihood of unemployment, reduced work productivity, poorer physical health etc. Negative outcomes associated with PTSD also extend to increased rates of suicide attempts, homelessness, substance use, and domestic violence. Approximately 20% of OEF/OIF Veterans have history of traumatic brain injury (TBI), mostly in the mild range of severity. Mild TBI – concussion, blow to the head resulting in loss of consciousness less than 30 minutes, alteration of consciousness/posttraumatic amnesia lasting less than 24 hours.

Expected recovery time from mild TBI is a return to baseline functioning within three months with complete resolution of TBI-related sequelae. But a significant minority report post-concussive symptoms including cognitive difficulties – higher rates of poorer recovery in military personnel compared to civilians. Research indicates that comorbid psychiatric conditions play a significant role in the persistence of symptoms and cognitive deficits in those with history of mTBI. They have poorer functional outcomes, greater severity of mental health and post-concussive symptoms, and decreased quality of life than those with either condition alone.

Cognitive Behavioural Therapy (CBT) is shown to be one of the most effective PTSD treatments and can reduce post-concussive symptoms in those with a history of mild-to-moderate TBI. Despite efforts by the VA/DoD to make evidence-based treatments available to Veterans with PTSD, a substantial portion of people drop out of treatment prematurely, don’t respond to it, or relapse after completion. Treatment engagement is worse for OEF/OIF Veterans – less likely to begin treatment, attend fewer sessions, and have higher dropout rates than civilians/Veterans form other eras. History of mild TBI may exacerbate these effects.

It’s hypothesized that a likely barrier to treatment completion/effectiveness is the executive function problems present in people with PTSD and history of TBI. EFs are a set of higher-level cognitive abilities that organize and integrate lower-level cognitive processes to guide behaviour and perform complex, goal-directed tasks. Three interrelated but distinct core EFs: shifting/cognitive flexibility, updating working memory, and inhibition – together contributing to other EFs (planning, problem solving, reasoning). EF is important for success in everyday life. EF deficits are associated with maladaptive behaviours and negative outcomes including substance use, crime, violence, recklessness, worse physical health, and poorer treatment adherence.

Neuropsychological research indicates that PTSD and history of TBI have (separately and jointly) been associated with EF deficits, including impairments in inhibitory control, working memory, task shifting, and sustained attention. Theories propose a bidirectional relationship between PTSD and EF – EF deficits contributing to development/maintenance of PTSD symptoms, and PTSD symptoms exacerbating EF impairments in turn. Also evidence that comorbid history of TBI increases risk for and contributes to EF deficits.

EF impairments make it difficult to overcome logistic barriers contributing to non-compliance and drop out of PTSD treatment. Executive dysfunction can make it difficult to plan and problem solve to overcome these barriers making it hard to attend appointments and complete treatment. Further, as CBT relies on adequate EF, deficits could hinder effectiveness of PTSD treatments. Particularly a concern for CBT approaches that’re primarily cognitive in nature like CPT – which involves identifying/challenging maladaptive trauma-related thoughts to alter their impact on behaviour. EFs are essential in CPT to engage in cognitive skills involved in treatment.

Worse EF at baseline has been associated with poorer response to CBT in psychosis and schizophrenia, generalized anxiety disorder, and obsessive compulsive disorder. Research on baselines measures of cognitive functioning predicting treatment responses is limited. The two relevant published studies to date regarding EF indicate mixed findings. One study found that neuropsychological measures of EF obtained before treatment didn’t predict response to CBT. Conversely, another study utilized fMRI and showed that dysfunction in prefrontal and cingulate regions during an EF task prior to treatment predict nonresponse to CBT for PTSD. No studies until now have studied if baseline EF deficits predict dropout and poorer treatment outcomes in people with comorbid PTSD and history of TBI.

This study examined whether neuropsychological measures of EF obtained prior to treatment would be associated with dropout and response to CPT in Veterans with PTSD and history of TBI. Secondary analysis of a randomized control trial of standard CPT vs modified CPT including compensatory rehabilitation strategies was performed. Hypothesis: worse baseline EF would be associated with reduced CPT completion and responsivity.

Method

Participants

Consisted of 74 participants who were 1) OEF/OIF Veterans with PTSD, 2) had a history of mild to moderate TBI, 3) reported current subjective cognitive complaints, and 4) were stable on psychiatric medication for at least six weeks.

Procedure

Participants were assessed for inclusion/exclusion criteria and provided informed consent for participation. They were randomized to one of two 12-week treatment conditions: 1) standard CPT or 2) SMART-CPT, novel hybrid treatment integrated psychoeducation about TBI and compensatory cognitive rehabilitation strategies from CogSMART into CPT. SMART-CPT included cognitive strategies focused on attention, memory, and executive functioning modified CPT to include more concrete language, repetition of key points via written summaries and brief reviews, and simplified/restructured worksheets.

Baseline assessment of study variables included measures of demographics, TBI characteristics, psychiatric and post-concussive symptoms, quality of life, and cognitive functioning. Participants completed a symptom measure of PTSD weekly during treatment to assess ongoing symptom change in addition to completing it during the three assessment visits.

Measures

• Symptom questionnaires
• Neuropsychological measures
• TBI characteristics
• Statistical analyses

Discussion

As hypothesized, poorer performance on baseline measures of EF associated with dropout and reduced responsivity to trauma-focused treatment in Veterans with PTSD and a history of mild-to-moderate TBI. Those who dropped out of treatment prematurely performed more poorly on EF tests of novel problem solving and shifting/cognitive flexibility at baseline, though only novel problem solving remained a significant predictor of dropout when controlling for baseline symptom severity. Worse baseline performances on EF tests were associated with poorer response to CPT. Finally, baseline measures of memory, intellectual functioning, and education weren’t associated with dropout or treatment response – indicating effects were specific to EF.

Findings are consistent with theory suggesting that executive dysfunction in people with PTSD and history of TBI may be a barrier to treatment completion and responsivity, especially for CPT as intact EFs are needed for successful use of CBT strategies. Worse EF (reduced cognitive flexibility), may be especially problematic for therapy approaches that predominantly involve cognitive restructuring such as CPT because reappraisal techniques rely heavily on executive process in order to inhibit maladaptive thoughts and beliefs and flexibility generate and evaluate alternative, more realistic thoughts. Problems with EFs can also lead to dropout of treatment because of difficulties utilizing planning and problem solving skills to overcome various logistic barriers that make it difficult to attend therapy appointments.

Adaptive motivational processing relies on intact EF so goals can be selected based on their predicted outcomes, behaviours can be planned to achieve these goals, and goal-directed action can be maintained in the face of distraction. So EF impairments may contribute to difficulty maintaining motivation to persist in treatment, especially when it becomes emotionally challenging. Motivational dysfunction can also manifest in therapy-interfering behaviours like missing sessions, avoiding assignments, and engaging in maladaptive coping strategies when in distress. EF deficits could contribute to difficulties flexibly planning and implementing strategies to overcome challenges to trauma-focused treatment in order to persist in long-term goal achievement.

Results also fit with previous empirical studies demonstrating that worse EF at baseline associates with dropout from CBT for substance dependence and generalized anxiety disorder, as well as reduced response to CBT in several psychiatric disorders.

Little research has considered whether poorer neuropsychological functioning in any cognitive domain at baseline reduces response to PTSD treatment. Few studies examining these possible relationships focused mainly on memory. Nonsignificant findings for memory (discrepant with previous studies) paired with significant results for EF suggest that relationships between aspects of cognition and treatment may depend on the type of treatment approach used.

These findings have several clinical implications. Assessing pre-treatment cognitive functioning, using low cost neuropsychological measures may inform efforts to better match individuals with treatments they’re most likely to benefit from. Also altering current PTSD treatments to use methods that more directly target executive dysfunction could improve treatment adherence and boost its effectiveness. Adding cognitive training to existing treatments has also increased mental health treatment completion rates. Thus taken together, results suggest that directly targeting EF via cognitive training before treatments like CPT could strengthen executive networks and allow Veterans to fully engage in and benefit more from components of CPT. Finally, results indicate that those with reduced cognitive flexibility benefit from modifications to CPT, including adding compensatory strategies and altering CPT to include more concrete language, repetition of key points, written summaries, and simplified worksheets.

Strengths:

• Use of multilevel modeling with 14 assessment time points – facilitating better modeling and estimation of treatment response.
• Contribution of baseline neuropsychological functioning to treatment completion and response were considered jointly, which has rarely been done previously, despite high dropout and nonresponse rate to PTSD treatment.
• Multiple EF measures included to examine different aspects of EF, given the importance of considering distinct EF’s separately.

Limitations:

• Limitations of this study may make it difficult to generalize findings to other populations.
• Sample was predominantly male veterans – unclear if results would be consistent for nonVeteran samples or female veterans.
• Also unclear if the same relationships would be observed in individuals with only PTSD (no history of TBI). It’s possible that observed relationships are somewhat unique to those with both conditions as these individuals often have more severe symptoms, worse executive abilities, and poorer functioning, leading to negative impact on treatment. But it was found that TBI characteristics weren’t associated with dropout from CPT and other studies have shown that presence of TBI history didn’t predict treatment response (though these samples were small).

Future research would benefit from larger samples to further explore the role of comorbid TBI history and associated injury characteristics in treatment compared to PTSD alone. But despite these limitations, this study makes important contributions to our understanding of relationships between baseline EF abilities and PTSD treatment completion/responsivity.